An organism as a biological system briefly. Organism as a biological system: features, functions and a brief theory. Modern ideas about the gene and genome
The concept of growth and development
The processes of growth and development are general biological properties of living matter. The growth and development of a person, starting from the moment of fertilization of the egg, is a continuous progressive process that takes place throughout his life. The process of development proceeds in leaps and bounds, and the difference between the individual stages, or periods, of life is reduced not only to quantitative, but also to qualitative changes. The presence of age-related features in the structure or activity of certain physiological systems can in no way be evidence of the inferiority of the child's body at certain age stages. This or that age is characterized by a complex of similar features. Development should be understood as the process of quantitative and qualitative changes occurring in the human body, leading to an increase in the level of complexity of the organization and interaction of all its systems.
Development includes three main factors: growth, differentiation of organs and tissues, shaping. One of the main physiological features of the human body that distinguishes a child from an adult is his height. Growth is a quantitative process characterized by a continuous increase in body weight, accompanied by a change in the number of body cells or their size. In some organs and tissues (bones, lungs), growth is carried out mainly due to an increase in the number of cells, in others (muscles, nervous tissue), the processes of increasing the size of the cells themselves predominate. Exclusion of those changes in mass due to body fat or water retention. A more accurate indicator of growth is an increase in the total amount of protein in it and an increase in bone size.
Development is a complex process of quantitative and qualitative changes occurring in the human body and leading to an increase in the level of complexity of the body and the interaction of all its systems. Development includes three main factors: growth, differentiation of organs and tissues, and shaping. Formation is a change in the proportions of a growing organism. The shape of the human body in different age periods is not the same. For example, the size of a newborn's head is? body length, at 5-7 years old - 1/6, in adults - 1/8. The length of the leg of a newborn is 1/3 of the length of the body, and an adult ?. The center of the body of the newborn is located in the umbilical ring. With the growth of the body, it shifts down to the pubic bone. The important patterns of growth and development of children include unevenness - heterochrony and continuity of growth and development, the phenomenon of advanced maturation of vital functional systems. P.K. Anokhin put forward the doctrine of heterochrony - uneven development and the doctrine of systemogenesis arising from it.
Heterochrony provides a harmonious relationship between the developing organism and the environment, i.e. those structures and functions are rapidly formed that ensure the adaptation of the organism, its survival
Systemogenesis is the study of functional systems. According to Anokhin's ideas, a functional system should be understood as a broad functional association of variously localized structures based on obtaining the final adaptive effect that is necessary at the moment (the system of the act of sucking, body movement). Functional systems mature unevenly, change, providing the body with adaptation in different periods of ontogenesis.
Periods of development of the body
The period of time during which the processes of growth, development and functioning of the body are identical, is called the age period. At the same time, it is a period of time necessary for the completion of a certain stage in the development of an organism and its readiness for a certain activity. This pattern of growth and development formed the basis of age periodization - the unification of emerging children, adolescents and adults by age.
Age periodization, combining specific anatomical and functional features of the body, is important in the medical, pedagogical, social, sports, economic and other fields of human activity.
Modern physiology considers the period of maturation of the body from the moment of fertilization of the egg and divides the entire development process into two stages:
1) intrauterine (prenatal) stage:
Embryonic development phase 0-2 months Fetal (fetal) development phase 3-9 months
2) extrauterine (postnatal) stage:
Neonatal period 0-28 days Infant period 28 days -1 year Early childhood period 1-3 years Preschool period 3-6 years School period: Junior 6-9 years Middle 10-14 years Senior 15-17 years Youth period: for boys 17 -21 years old for girls 16-20 years old age: 1st period for men 22-35 years old 1st period for women 21-35 years old 2nd period for men 36-60 years old 2nd period for women 36-55 years old age: men 61 - 74 years old women 56 - 74 years old senile age 75 - 90 years old long-livers 90 years old or more.
Periodization criteria are signs regarded as an indicator of biological age: body and organ size, weight, ossification of the skeleton, teething, development of endocrine glands, degree of puberty, muscle strength. This scheme takes into account the characteristics of boys and girls. Each age period has its own characteristics.
The transition from one period to another is considered a critical period. The duration of individual age periods varies. 5. Critical periods of a child's life The development of the organism of the fetus during 8 weeks of pregnancy is characterized by increased sensitivity to various internal and external factors. Critical periods are considered: the time of fertilization, implantation, organogenesis and the formation of the placenta (these are internal factors).
External factors include: mechanical, biological (viruses, microorganisms), physical (radiation), chemical. A change in the internal connections of the embryo and a violation of external conditions can lead to a delay or halt in the development of individual parts of the embryo. In such cases, congenital anomalies are observed up to the death of the embryo. The second critical period of intrauterine development is considered: the time of intensive brain growth (4.5 - 5 months of pregnancy); completion of the formation of the function of body systems (6 months of pregnancy); moment of birth. The first critical period of extrauterine development is from 2 to 3 years, when the child begins to actively move. The sphere of his communication with the outside world is expanding sharply, speech and consciousness are being intensively formed. By the end of the second year of life, the child's vocabulary contains 200-400 words. He eats independently, regulates urination and defecation. All this leads to stress on the physiological systems of the body, which especially affects the nervous system, the overstrain of which can lead to mental development disorders and diseases.
The passive immunity received from the mother is weakened; against this background, infections can occur, which leads to anemia, rickets, diathesis. The second critical period, at 6-7 years old, the school enters the life of the child, new people, concepts, responsibilities appear. New demands are placed on the child. The combination of these factors causes an increase in tension in the work of all body systems that adapt the child to new conditions. There are differences in the development of girls and boys. Only in the middle of the school period (by the age of 11-12) does the larynx grow in boys, the voice changes, and the genitals take shape.
Girls are ahead of boys in height and body weight. The third critical period is associated with a change in the body's hormonal balance. Deep restructuring, occurring at 12-16 years old, is due to the relationship of the endocrine glands of the hypothalamic-pituitary system. Pituitary hormones stimulate the growth of the body, the activity of the thyroid gland, adrenal glands and gonads. There is an imbalance in the development of internal organs: the growth of the heart outstrips the growth of blood vessels. High pressure in the vessels and the rapid development of the reproductive system lead to heart failure, dizziness, fainting, and increased fatigue.
The emotions of adolescents are changeable: sentimentality borders on hypercriticism, swagger and negativism. A teenager develops a new idea of himself as a person. The development of children in different periods of ontogenesis.
The influence of heredity and environment on the development of the child
1. Physical development is an important indicator of health and social well-being. Anthropometric studies to assess physical development
2. Characteristics of the anatomical and physiological characteristics of children in different periods of ontogenesis
3. The influence of heredity and environment on the development of the child
4. Biological acceleration
Physical development is an important indicator of health and social well-being
The main indicators of physical development are body length, weight and chest circumference. However, when evaluating the physical development of a child, they are guided not only by these somatic values, but also use the results of physiometric measurements (vital capacity of the lungs, grip strength of the hand, back strength) and somatoscopic indicators (development of the musculoskeletal system, blood supply, fat deposition, sexual development, various deviations in physique).
Guided by the totality of these indicators, it is possible to establish the level of physical development of the child. Anthropometric studies of children and adolescents are included not only in the program of studying physical development and health status, but are also often carried out for applied purposes: to determine the size of clothes and shoes, equipment for children's educational and educational institutions.
Characteristics of the anatomical and physiological characteristics of children in different periods of ontogenesis
Each age period is characterized by quantitatively determined morphological and physiological parameters. The intrauterine stage of human development lasts 9 calendar months. The main processes of formation and development of a new organism are divided into two phases: embryonic and fetal development. The first phase of embryonic development lasts from the moment of fertilization to 8 weeks of pregnancy. As a result of fertilization, an embryo is formed - a zygote. Cleavage of the zygote within 3-5 days leads to the formation of a multicellular vesicle - blastula. On the 6-7th day, the zygote implants (immerses) into the thickness of the uterine mucosa.
During 2-8 weeks of pregnancy, the formation of organs and tissues of the embryo continues. At the age of 30 days, the embryo develops lungs, a heart, a neural and intestinal tube, and the rudiments of hands appear. By the 8th week, the laying of the organs of the embryo ends: the brain and spinal cord, outer ear, eyes, eyelids, fingers are indicated, the heart beats at a frequency of 140 beats per minute; With the help of nerve fibers, a connection is established between organs. It persists until the end of life. At this stage, the formation of the placenta is completed. The second phase of embryonic development - the fetal phase lasts from the 9th week of pregnancy until the birth of the child. It is characterized by rapid growth and differentiation of the tissues of the organs of the growing fetus, primarily the nervous system.
Fetal nutrition is provided by the placental circulation. The placenta, as an organ that carries out metabolic processes between the blood of the mother and the fetus, is at the same time a biological barrier for some toxic substances. But through the placenta, drugs, alcohol, nicotine penetrate into the bloodstream. The use of these substances significantly reduces the barrier function of the placenta, which leads to fetal disease, malformations and death. The extrauterine stage of human development of its organs and systems occurs unevenly.
The neonatal period is the time when a newborn child adapts to a new environment. Pulmonary respiration occurs, changes occur in the circulatory system, the nutrition and metabolism of the child completely changes. However, the development of a number of organs and systems of the newborn has not yet been completed, and therefore all functions are weak. Characteristic signs of this period are fluctuations in body weight, violation of thermoregulation. The head of the newborn is large, rounded, is? body length. The neck and chest are short, and the belly is elongated; the brain part of the skull is larger than the facial part, the shape of the chest is bell-shaped. The pelvic bones are not fused together. The internal organs are relatively larger than in adults. During infancy, the body grows most rapidly.
At birth, the average child weighs 3-3.5 kg, and the length is approximately equal to the distance from the elbow to the fingertips. By two, the height of the child will be half of his height in adulthood. In the first six months your baby will probably gain 550-800g in weight and about 25mm in length each month. Little children don't just grow, they grow upwards. Between six months and a year, everything changes in a child. At birth, his muscles are weak. Its bones are brittle and its brain, in a tiny head, is very small. He still regulates his body temperature, blood pressure and breathing very poorly. He knows almost nothing and understands even less. By his first birthday, his bones and muscles change structure, his heart beats faster, he is able to control his breathing, and his brain has grown in size. Now he walks holding on to a support, gasping for air before screaming, playing patty, and almost always stops when you say “No.”
Girls develop somewhat faster than boys. Physical disabilities can have a very significant impact on the development of many skills and abilities of a child in the first year of life: for example, it will be more difficult for a blind child to learn to walk and talk. The period of early childhood. The first skills and abilities appear by 1.5 years. The child knows how to eat from a spoon, takes a cup and drinks from it. During this period, the increase in body weight outstrips the growth in length. All milk teeth erupt. Rapid motor development is noted. The thumb is opposed to the rest. Grasping movements are improved. Preschool period. During this period, growth in length accelerates. The movements of the child are more coordinated and complex. He can walk for a long time. In games, it reproduces a series of sequential actions. The mass of the brain of a five-year-old child is 85-90% of the mass of the brain of an adult. The degree of sensory development is much higher: the child, at the request, collects identical-looking objects, distinguishes between the sizes and colors of toys. Understands spoken words very well. The picture can answer the question. If at the beginning of the period the child pronounces light words, then by the end of it he can make a complex sentence.
Speech develops rapidly. Lack of development of motor skills of speech can lead to violations in pronunciation. At the end of the period, a change in the dynasty of teeth begins. Diseases of this period are associated mainly with viral diseases. In preschool years, the child grows every year by 50-75 mm and gains about 2.6 kg of weight. The greatest amount of fat is deposited by 9 months, after which the child loses weight.
Your child's bones will grow as the bones of the limbs grow faster than the bones of the torso, the proportions of the child's body will change. The number of small bones of the wrist increases. By the age of two, the fontanel will close. The brain at the time of development does not have enough connections between cells, and not all cells are in their place. First they move to their place, and then they begin to establish connections. In the process, the brain increases its weight from 350g to 1.35kg, mostly in the first two or three years of life. Along with the formation of relationships, the brain destroys those that it no longer needs. At the same time, the process of myelination occurs (the formation of a myelin sheath around the processes of nerve cells). Myelin is a fatty sheath that covers nerves, much like the plastic insulation on electrical cables, allowing impulses to travel faster. In multiple sclerosis, the myelin sheath ruptures, so you can imagine its importance.
The school period is divided into three stages and lasts up to 17 years. During this period, most of the processes of formation of the grown organism come to an end. During school years, the child continues to grow and develop. A jump in growth and development occurs in adolescence - this is a period of 10-12 years. During this period, there are difficult perestroika moments in the development of a teenager. At primary school age, the body is rounded. In girls, the pelvis expands, the hips are rounded. Teenage years. The physical changes that indicate a child is becoming an adult appear earlier in girls than in boys. On average, girls and boys are the same height and weight until about 11 years of age; when the girls begin to grow rapidly up. This difference persists for about two years, after which the boys also experience a growth spurt, they catch up and surpass the girls in height and maintain this height and weight for a long time. During puberty, secondary sexual characteristics are formed.
Adolescence is the period of completion of the growth and development of the body, the functional characteristics of which are as close as possible to the characteristics of the body of an adult. The processes of adaptation of the individual to the environment are also being completed. A sense of independence develops. Children of this age are on the threshold of transition from biological to social maturity. In adulthood, the structure of the body changes little.
The first stage of this age is an active personal life and professional activity, the second is the time of the greatest opportunities for a person enriched with life experience, knowledge, and professionalism.
In the elderly and senile age, there is a decrease in the adaptive capabilities of the body, the morphological and functional parameters of all systems change, especially the immune, nervous and circulatory ones. These changes are studied by the science of gerontology.
The influence of heredity and environment on the development of the child
The development of the child is influenced by biological factors - heredity, possible birth trauma, poor or good health. But the environment also plays a role - the love and stimulation the child receives; what is happening in his life; where does it grow? how his family and friends treat him. The development of the child also has a type of temperament, self-confidence. Some aspects of development are more hereditary than others. Physical development usually occurs strictly according to the schedule. If the environment and nutrition are normal, it occurs according to nature's prescription. The child starts talking no matter what you do. Most children master the ability to communicate by the age of five. Heredity is divided into favorable and unfavorable. The inclinations that ensure the harmonious development of the abilities and personality of the child belong to favorable heredity. If the appropriate conditions are not created for the development of these inclinations, then they fade away, not reaching the level of development of the parents' giftedness. A burdened heredity cannot ensure the normal development of a child.
The reason for the abnormal development of children may be alcoholism or the harmfulness of the profession of parents (for example, work related to radioactive substances, poisons, vibration). In some cases, unfavorable heredity can be corrected and managed. For example, treatments for hemophilia have been developed. The organism is not possible without the environment, therefore, environmental factors affecting the development of the organism must be taken into account. In this regard, reflexes are reactions of the body's constant adaptation to the outside world. The development of a person cannot be adequately assessed without taking into account the environment in which he lives, works, is brought up, with whom he communicates, and the functions of the body - without taking into account the hygienic requirements for the workplace, home environment, without taking into account relationships with plants, animals, etc.
Biological acceleration
Acceleration is the acceleration of the growth and development of children and adolescents compared to previous generations. The phenomenon of acceleration is observed primarily in economically developed countries. The term acceleration was introduced by E. Koch. Most researchers have expanded the concept of acceleration and began to understand it as an increase in body size and the onset of maturation at an earlier date. In connection with acceleration, growth also ends earlier. At 16-17 years old in girls and at 18-19 years old in boys, ossification of long tubular bones is completed and growth in length stops. Over the past 80 years, Moscow boys aged 13 have become 1 cm taller, and girls 14.8 cm taller. As a result of the accelerated development of children and adolescents, they are achieving higher rates of physical development.
There is information about the lengthening of the childbearing period: over the past 60 years, it has increased by 8 years. For women in Central Europe over the past 100 years, menopause has shifted from 45 to 48 years, in our country this time is an average of 50 years, and at the beginning of the century it was 43.7 years. Until now, there is no generally accepted point of view on the origin of the acceleration process. Some scientists associate acceleration with an increase in the content of high-grade proteins and natural fats in food, as well as with a more regular consumption of vegetables and fruits throughout the year, enhanced fortification of the body of the mother and child. There is a heliogenic theory of acceleration. In it, an important role is given to the effect of sunlight on the child: it is believed that children are now more exposed to solar radiation. However, this conclusion is not convincing enough, because the process of acceleration in the northern countries is no slower than in the south. Acceleration is also associated with climate change: it is believed that humid and warm air slows down the process of growth and development, and a cool, dry climate contributes to the loss of heat by the body, which stimulates growth. In addition, there is evidence of a stimulating effect on the body of small doses of ionizing radiation.
Some scientists believe that the acceleration is due to the development of medicine: a general decrease in morbidity and improved nutrition. Many new chemicals have appeared, the effect on the body of which is not well understood. Associate acceleration with the advent of artificial lighting. At night, in settlements, houses are lit, streets are lit with lanterns, light from shop windows, etc., all this leads to a decrease in the inhibitory effect of the hormone melatonin, which is released only in the dark, on the function of the pituitary gland, which leads to increased release growth hormone, stress hormones, sex hormones, which is manifested in teenage acceleration. There is nothing wrong with acceleration itself. But often it is disharmonious. Acceleration disharmony manifests itself in adolescents in such anatomical, physiological and psychological phenomena as disproportionate growth, early puberty, early obesity, hyperthyroidism (enlargement of the thyroid gland), increased aggressive reactions during frustration. Acceleration is a subject of study in biology, medicine, pedagogy, psychology, and sociology. So experts note the gap between biological and social maturity, the first comes earlier. There is a need to define new standards of labor and physical activity in schools, nutrition standards, standards for children's clothing, shoes, and furniture.
The organism as a biological system
3.2. Reproduction of organisms, its significance. Methods of reproduction, similarities and differences between sexual and asexual reproduction. The use of sexual and asexual reproduction in human practice. The role of meiosis and fertilization in ensuring the constancy of the number of chromosomes in generations. Application of artificial insemination in plants and animals
asexual reproduction, vegetative reproduction, hermaphroditism, zygote, ontogenesis, fertilization, parthenogenesis, sexual reproduction, budding, spores.
reproduction in the organic world. The ability to reproduce is one of the most important signs of life. This ability is manifested already at the molecular level of life. Viruses, penetrating into the cells of other organisms, reproduce their DNA or RNA and thus multiply. reproduction- this is the reproduction of genetically similar individuals of a given species, ensuring the continuity and continuity of life.
There are the following forms of reproduction:
Asexual reproduction. This form of reproduction is characteristic of both unicellular and multicellular organisms. However, asexual reproduction is most common in the kingdoms Bacteria, Plants, and Fungi. In the kingdom Among animals, mainly protozoa and intestinal cavities reproduce in this way.
There are several ways of asexual reproduction:
– Simple division of the mother cell into two or more cells. This is how all bacteria and protozoa reproduce.
- Vegetative reproduction by parts of the body is characteristic of multicellular organisms - plants, sponges, coelenterates, some worms. Plants can propagate vegetatively by cuttings, layering, root offspring and other parts of the body.
- Budding - one of the options for vegetative reproduction is characteristic of yeast and intestinal multicellular animals.
– Mitotic sporulation is common among bacteria, algae, and some protozoa.
Asexual reproduction usually provides an increase in the number of genetically homogeneous offspring, so it is often used by plant breeders to preserve the useful properties of the variety.
sexual reproduction A process in which genetic information from two individuals is combined. Combining genetic information can occur when conjugation (temporary connection of individuals for the exchange of information, as occurs in ciliates) and copulation (fusion of individuals for fertilization) in unicellular animals, as well as during fertilization in representatives of different kingdoms. A special case of sexual reproduction is parthenogenesis in some animals (aphids, drone bees). In this case, a new organism develops from an unfertilized egg, but before that, the formation of gametes always occurs.
Sexual reproduction in angiosperms occurs by double fertilization. The fact is that haploid pollen grains are formed in the anther of the flower. The nuclei of these grains are divided into two - generative and vegetative. Once on the stigma of the pistil, the pollen grain germinates, forming a pollen tube. The generative nucleus divides again, forming two sperm. One of them, penetrating into the ovary, fertilizes the egg, and the other merges with the two polar nuclei of the two central cells of the embryo, forming a triploid endosperm.
During sexual reproduction, individuals of different sexes form gametes. Females produce eggs, males produce sperm, and bisexual individuals (hermaphrodites) produce both eggs and sperm. In most algae, two identical germ cells merge. Fusion of haploid gametes results in fertilization and the formation of a diploid zygote. The zygote develops into a new individual.
All of the above is true only for eukaryotes. Prokaryotes also have sexual reproduction, but it happens in a different way.
Thus, during sexual reproduction, the genomes of two different individuals of the same species are mixed. Offspring carry new genetic combinations that distinguish them from their parents and from each other. Various combinations of genes that appear in the offspring in the form of new traits of interest to humans are selected by breeders to develop new breeds of animals or plant varieties. In some cases, artificial insemination is used. This is done both in order to obtain offspring with the desired properties, and in order to overcome the childlessness of some women.
EXAMPLES OF TASKS Part AA1. The fundamental differences between sexual and asexual reproduction are that sexual reproduction:
1) occurs only in higher organisms
2) this adaptation to adverse environmental conditions
3) provides combinative variability of organisms
4) ensures the genetic constancy of the species
A2. How many spermatozoa are formed as a result of spermatogenesis from two primary germ cells?
1) eight 2) two 3) six 4) four
A3. The difference between oogenesis and spermatogenesis is that:
1) four equivalent gametes are formed in oogenesis, and one in spermatogenesis
2) eggs contain more chromosomes than sperm
3) in oogenesis, one full-fledged gamete is formed, and in spermatogenesis - four
4) oogenesis takes place with one division of the primary germ cell, and spermatogenesis - with two
A4. How many divisions of the original cell occur during gametogenesis
1) 2 2) 1 3) 3 4) 4
A5. The number of germ cells formed in the body, most likely, may depend on
1) supply of nutrients in the cell
2) the age of the individual
3) the ratio of males and females in the population
4) the probability of meeting gametes with each other
A6. Asexual reproduction dominates the life cycle
1) hydras 3) sharks
A7. Gametes in ferns are formed
1) in sporangia 3) on leaves
2) on the growth 4) in disputes
A8. If the diploid set of chromosomes of bees is 32, then 16 chromosomes will be contained in somatic cells
1) queen bee
2) worker bee
3) drones
4) all listed individuals
A9. Endosperm in flowering plants is formed by fusion
1) sperm and eggs
2) two sperm and an egg
3) polar nucleus and sperm
4) two polar nuclei and sperm
A10. Double fertilization occurs in
1) cuckoo flax moss 3) medicinal chamomile
2) bracken fern 4) common pine
Part BIN 1. Choose the right statements
1) The formation of gametes in plants and animals occurs according to one mechanism
2) All types of animals have eggs of the same size
3) Fern spores are formed as a result of meiosis
4) 4 eggs are formed from one oocyte
5) The egg of an angiosperm is fertilized by two sperm
6) The endosperm of angiosperms is triploid.
IN 2. Establish a correspondence between the forms of reproduction and their characteristics
VZ. Set the correct sequence of events that occur during double fertilization of flowering plants.
A) fertilization of the egg and the central cell
B) the formation of a pollen tube
B) pollination
D) the formation of two sperm
D) development of the embryo and endosperm
Part CC1. Why is the endosperm of angiosperms triploid, while the rest of the cells are diploid?
C2. Find the errors in the given text, indicate the numbers of the sentences in which they are made, and correct them. 1) Diploid pollen grains are formed in the anthers of angiosperms. 2) The nucleus of the pollen grain is divided into two nuclei: vegetative and generative. 3) The pollen grain falls on the stigma of the pistil and germinates towards the ovary. 4) In the pollen tube, two sperm are formed from the vegetative nucleus. 5) One of them merges with the nucleus of the egg, forming a triploid zygote. 6) Another sperm fuses with the nuclei of the central cells, forming the endosperm.
3.3. Ontogeny and its inherent regularities. Specialization of cells, formation of tissues, organs. Embryonic and postembryonic development of organisms. Life cycles and alternation of generations. Causes of impaired development of organisms
Ontogenesis. Ontogenesis - this is the individual development of the organism from the moment of formation of the zygote to death. In the course of ontogenesis, a regular change in phenotypes characteristic of a given species is manifested. Distinguish indirect And straight ontogenesis. indirect development(metamorphosis) occurs in flatworms, molluscs, insects, fish, amphibians. Their embryos go through several stages in their development, including the larval stage. direct development takes place in a non-larval or intrauterine form. It includes all forms of ovoviviparity, the development of the embryos of reptiles, birds and oviparous mammals, as well as the development of some invertebrates (Orthoptera, arachnids, etc.). Intrauterine development occurs in mammals, including humans. IN ontogeny distinguish two periods embryonic - from the formation of a zygote to release from the egg membranes and postembryonic from the moment of birth to death. Embryonic period a multicellular organism consists of the following stages: zygotes; blastula- stages of development of a multicellular embryo after crushing the zygote. The zygote in the process of blastulation does not increase in size, the number of cells of which it consists increases; stages of formation of a single-layered embryo, covered blastoderm, and the formation of the primary body cavity - blastoceles; gastrulae- stages of formation of germ layers - ectoderm, endoderm (in two-layer coelenterates and sponges) and mesoderm (in three-layer in other multicellular animals). In intestinal animals, specialized cells are formed at this stage, such as stinging, genital, skin-muscular, etc. The process of gastrula formation is called gastrulation.
Neirula- Stages of laying individual organs.
Histo- and organogenesis- the stage of appearance of specific functional, morphological and biochemical differences between individual cells and parts of the developing embryo. In Vertebrate animals in organogenesis it is possible to distinguish:
a) neurogenesis - the process of formation of the neural tube (brain and spinal cord) from the ectodermal germ layer, as well as the skin, organs of vision and hearing;
b) chordogenesis - the process of formation from mesoderm chords, muscles, kidneys, skeleton, blood vessels;
c) the process of formation from endoderm intestines and related organs - liver, pancreas, lungs. The successive development of tissues and organs, their differentiation occurs due to embryonic induction- the influence of some parts of the embryo on the development of other parts. This is due to the activity of proteins that are included in the work at certain stages of the development of the embryo. Proteins regulate the activity of genes that determine the characteristics of an organism. Thus, it becomes clear why the signs of a certain organism appear gradually. All genes are never put to work together. At a particular time, only a part of the genes work.
Postembryonic period is divided into the following steps:
- postembryonic (before puberty);
- the period of puberty (implementation of reproductive functions);
- aging and death.
In humans, the initial stage of the postembryonic period is characterized by the intensive growth of organs and body parts in accordance with established proportions. In general, the postembryonic period of a person is divided into the following periods:
- infants (from birth to 4 weeks);
- chest (from 4 weeks to a year);
- preschool (nursery, middle, senior);
- school (early, teenage);
- reproductive (young up to 45 years old, mature up to 65 years old);
- post-reproductive (elderly up to 75 years and senile - after 75 years).
EXAMPLES OF TASKSPart BUTA1. The two-layer structure of the flow is characteristic of
1) annelids 3) coelenterates
2) insects 4) protozoa
A2. no mesoderm
1) earthworm 3) coral polyp
A3. Direct development occurs in
1) frogs 2) locusts 3) flies 4) bees
A4. As a result of cleavage of the zygote, a
1) gastrula 3) neurula
2) blastula 4) mesoderm
A5. Develops from the endoderm
1) aorta 2) brain 3) lungs 4) skin
A6. Separate organs of a multicellular organism are laid down at the stage
1) blastula 3) fertilization
2) gastrula 4) neurula
A7. Blastulation is
1) cell growth
2) multiple crushing of the zygote
3) cell division
4) an increase in the size of the zygote
A8. The gastrula of the dog embryo is:
1) an embryo with a formed neural tube
2) multicellular single-layer embryo with a body cavity
3) multicellular three-layer embryo with a body cavity
4) multicellular two-layer embryo
A9. Differentiation of cells, organs and tissues occurs as a result of
1) the actions of certain genes at a certain time
2) simultaneous action of all genes
3) gastrulation and blastulation
4) development of certain organs
A10. What stage of embryonic development of vertebrates is represented by a multitude of unspecialized cells?
1) blastula 3) early neurula
2) gastrula 4) late neurula
Part BIN 1. Which of the following refers to embryogenesis?
1) fertilization 4) spermatogenesis
2) gastrulation 5) crushing
3) neurogenesis 6) oogenesis
IN 2. Select the features characteristic of blastula
1) an embryo in which a chord is formed
2) multicellular embryo with a body cavity
3) an embryo consisting of 32 cells
4) three-layer embryo
5) a single-layer embryo with a body cavity
6) an embryo consisting of a single layer of cells
VZ. Match the organs of a multicellular embryo with the germ layers from which these organs are formed.
C1. Give examples of direct and indirect postembryonic development on the example of insects.
3.4. Genetics, its tasks. Heredity and variability are properties of organisms. Basic genetic concepts
allelic genes, analyzing crossing, gene interaction, gene, genotype, heterozygosity, gamete purity hypothesis, homozygosity, dihybrid crossing, G. Mendel's laws, quantitative traits, crossing over, flying, multiple alleles, monohybrid crossing, independent inheritance, incomplete dominance, uniformity rule , splitting, phenotype, cytological basis of Mendel's laws.
Genetics- the science of heredity and variability of organisms. These two properties are inextricably linked with each other, although they have opposite directions. Heredity involves the preservation of information, and variability changes this information. Heredity- this is the property of an organism to repeat its signs and features of its development in a number of generations. Variability is the property of organisms to change their characteristics under the influence of the external or internal environment, as well as as a result of new genetic combinations that occur during sexual reproduction. The role of variability lies in the fact that it "supplies" new genetic combinations that are subject to the action of natural selection, and heredity preserves these combinations.
The main genetic concepts include the following:
Gene- a section of a DNA molecule that encodes information about the sequence of amino acids in one protein molecule.
allele- a pair of genes responsible for an alternative (different) manifestation of the same trait. For example, two allelic genes located in the same loci (places) of homologous chromosomes are responsible for eye color. Only one of them can be responsible for the development of brown eyes, and the other for the development of blue eyes. In the case when both genes are responsible for the same development of a trait, they speak of homozygous organism on this basis. If allelic genes determine the different development of a trait, they talk about heterozygous body.
Allelic genes can be dominant that suppress the alternative gene, and recessive , suppressed.
The totality of an organism's genes is called genotype of this organism. The genotype of an organism is described by the words - "homozygous" or "heterozygous". However, not all genes are expressed. The totality of the external features of an organism is called its phenotype. Brown-eyed, full, tall is a way of describing the phenotype of an organism. They also talk about a dominant or recessive phenotype.
Genetics studies the patterns of inheritance of traits. The main method of genetics is the hybridological method or crossing. This method was developed by the Austrian scientist Gregor Mendel in 1865.
The development of genetics has led to the development of many scientific areas and, above all, evolutionary theory, plant and animal breeding, medicine, biotechnology, pharmacology, etc.
At the turn of the 20th and 21st centuries, the human genome was deciphered. Scientists were amazed that we have only 35,000 genes, and not 100,000, as previously thought. A roundworm has 19,000 genes, while mustard has 25,000. The differences between humans and chimpanzees are 1% of the genes, and with the mouse, 10%. Man also inherited genes that are 3 billion years old and relatively young genes.
What does reading the genome give science? First of all, this knowledge allows targeted genetic research to identify both pathological and necessary, useful genes. Scientists do not leave hope for curing people from such diseases as cancer and AIDS, diabetes, etc. They also do not leave hope for overcoming decrepit old age, premature death and many other troubles of mankind.
3.5. Patterns of heredity, their cytological basis. Mono- and dihybrid crossing. Patterns of inheritance established by G. Mendel. Linked inheritance of traits, violation of the linkage of genes. Laws of T. Morgan. Chromosomal theory of heredity. Sex genetics. Inheritance of sex-linked traits. The genotype as an integral system. Development of knowledge about the genotype. The human genome. Interaction of genes. Solution of genetic problems. Drawing up cross-breeding schemes. G. Mendel's laws and their cytological foundations
Terms and concepts tested in the examination paper: allelic genes, analyzing crossing, gene, genotype, heterozygosity, gamete purity hypothesis, homozygosity, dihybrid crossing, Mendel's laws, monohybrid crossing, morganide, heredity, independent inheritance, incomplete dominance, uniformity rule, splitting, phenotype, chromosome theory of heredity, cytological bases Mendel's laws.
The success of Gregor Mendel's work was due to the fact that he correctly chose the object of study and followed the principles that became the basis of the hybridological method:
1. The object of the study was pea plants belonging to the same species.
2. Experimental plants clearly differed in their characteristics - high - low, with yellow and green seeds, with smooth and wrinkled seeds.
3. The first generation from the original parent forms has always been the same. Tall parents produced tall offspring, short parents produced small plants. Thus, the original varieties were the so-called "pure lines".
4. G. Mendel kept a quantitative account of the descendants of the second and subsequent generations, in whom splitting in traits was observed.
The laws of G. Mendel describe the nature of the inheritance of individual traits over several generations.
Mendel's first law or the rule of uniformity. The law was derived on the basis of statistical data obtained by G. Mendel when crossing different varieties of peas, which had clear alternative differences in the following characteristics:
– seed shape (round / non-round);
- seed color (yellow / green);
– seed coat (smooth / wrinkled), etc.
When crossing plants with yellow and green seeds, Mendel found that all hybrids of the first generation were with yellow seeds. He called this trait dominant. The trait that determines the green color of the seeds was called recessive (receding, suppressed).
Since the examination work requires students to be able to correctly draw up notes when solving genetic problems, we will show an example of such a record.
1. Based on the results obtained and their analysis, Mendel formulated his first law. When crossing homozygous individuals that differ in one or more pairs of alternative traits, all hybrids of the first generation will be uniform in these traits and similar to the parent with a dominant trait.
When incomplete dominance only 25% of individuals are phenotypically similar to a parent with a dominant trait and 25% of individuals will be similar to a phenotype recessive parent. The remaining 50% of heterozygotes will be phenotypically different from them. For example, from red-flowered and white-flowered snapdragons in the offspring, 25% of individuals are red, 25% are white, and 50% are pink.
2. To identify the heterozygosity of an individual for a certain allele, i.e. the presence of a recessive gene in the genotype is used analyzing cross. For this, an individual with a dominant trait (AA? or Aa?) is crossed with an individual homozygous for the recessive allele. In the case of heterozygosity of an individual with a dominant trait, the splitting in the offspring will be 1: 1
AA? aa > 100% Aa
ah? aa > 50% Aa and 50% aa
Mendel's second law or splitting law. When crossing heterozygous hybrids of the first generation with each other, in the second generation, splitting according to this trait is detected. This splitting is of a natural statistical nature: 3: 1 in terms of phenotype and 1: 2: 1 in terms of genotype. In the case of crossing forms with yellow and green seeds, in accordance with Mendel's second law, the following crossing results are obtained.
Seeds appear with both yellow and green color.
Mendel's third law or the law of independent inheritance in dihybrid (polyhybrid) crossing. This law was derived on the basis of an analysis of the results obtained by crossing individuals that differ in two pairs of alternative traits. For example: a plant that gives yellow, smooth seeds are crossed with a plant that produces green, wrinkled seeds.
For further notation, the Punnett lattice is used:
In the second generation, 4 phenotypes may appear in a ratio of 9: 3: 3: 1 and 9 genotypes.
As a result of the analysis, it turned out that the genes of different allelic pairs and their corresponding traits are transmitted independently of each other. This law is correct:
– for diploid organisms;
– for genes located on different homologous chromosomes;
- with independent divergence of homologous chromosomes in meiosis and their random combination during fertilization.
These conditions are the cytological basis of dihybrid crossing.
The same patterns apply to polyhybrid crosses.
In Mendel's experiments, the discreteness (discontinuity) of hereditary material was established, which later led to the discovery of genes as elementary material carriers of hereditary information.
In accordance with the hypothesis of the purity of gametes, only one of the homologous chromosomes of a given pair is always in the norm in a sperm or egg. That is why, during fertilization, the diploid set of chromosomes of the given organism is restored. Split is the result of a random combination of gametes carrying different alleles.
Since the events are random, the pattern is statistical in nature, i.e. is determined by a large number of equally probable events - meetings of gametes carrying different (or identical) alternative genes.
EXAMPLES OF TASKS Part AA1. The dominant allele is
1) a pair of identical genes
2) one of two allelic genes
3) a gene that suppresses the action of another gene
4) repressed gene
A2. A part of a DNA molecule is considered a gene if it encodes information about
1) several signs of the body
2) one sign of the organism
3) several proteins
4) tRNA molecule
A3. If the trait does not appear in hybrids of the first generation, then it is called
1) alternative
2) dominant
3) not completely dominant
4) recessive
A4. Allelic genes are located in
1) identical sections of homologous chromosomes
2) different parts of homologous chromosomes
3) identical regions of non-homologous chromosomes
4) different parts of non-homologous chromosomes
A5. Which entry reflects a diheterozygous organism:
1) AABB 2) AaBv 3) AaBvSs 4) aaBBss
A6. Determine the phenotype of a pumpkin with the CC BB genotype, knowing that white color dominates over yellow, and disc-shaped fruits dominate over spherical
1) white, spherical 3) yellow discoid
2) yellow, spherical 4) white, discoid
A7. What offspring will result from crossing a polled (hornless) homozygous cow (horned bull gene B dominates) with a horned bull.
3) 50% BB and 50% BB
4) 75% BB and 25% BB
A8. In humans, the gene for protruding ears (A) dominates the gene for normally flattened ears, and the gene for non-red (B) hair dominates the gene for red hair. What is the genotype of a lop-eared, red-haired father, if, in a marriage with a non-red woman with normally flattened ears, he had only lop-eared, non-red children?
1) AABB 2) AaBB 3) AABB 4) AABB
A9. What is the probability of having a blue-eyed (a), fair-haired (c) child from the marriage of a blue-eyed, dark-haired (B) father and a brown-eyed (A), fair-haired mother, heterozygous for dominant traits?
1) 25% 2) 75% 3) 12,5% 4) 50%
A10. Mendel's second law is the law that describes the process
1) linkage of genes
2) mutual influence of genes
3) feature splitting
4) independent distribution of gametes
A11. How many types of gametes does an organism form with the AABvCs genotype
1) one 2) two 3) three 4) four
Part CC1. Determine the possible genotypes of the parents and five children, among whom were children with Roman and straight noses, full and thin lips, if it is known that a man with a Roman nose and thin lips married a girl with a Roman nose and full lips. Prove your answer by writing the solution of the problem in the form of two crossover schemes. How many crossover schemes can be analyzed in solving this problem?
Chromosomal theory of heredity. The founder of the chromosome theory Thomas Gent Morgan, American geneticist, Nobel laureate. Morgan and his students found that:
- each gene has a specific locus(a place);
- the genes in the chromosome are located in a certain sequence;
- the most closely located genes of one chromosome are linked, therefore they are inherited mainly together;
- groups of genes located on the same chromosome form linkage groups;
– the number of linkage groups is haploid set of chromosomes in homogametic individuals and n+1 heterogametic individuals;
- between homologous chromosomes, there can be an exchange of regions ( crossing over); as a result of crossing over, gametes arise, the chromosomes of which contain new combinations of genes;
– the frequency (in %) of crossing over between non-allelic genes is proportional to the distance between them;
is the set of chromosomes in cells of this type ( karyotype) is a characteristic feature of the species;
- the frequency of crossing over between homologous chromosomes depends on the distance between genes located on the same chromosome. The greater this distance, the higher the crossover frequency. One unit of distance between genes is taken as 1 morganid (1% of crossing over) or the percentage of occurrence of crossover individuals. With a value of this value of 10 morganids, it can be argued that the frequency of chromosome crossing at the points of location of these genes is 10% and that new genetic combinations will be revealed in 10% of the offspring.
To determine the nature of the location of genes in chromosomes and determine the frequency of crossing over between them, genetic maps are built. The map reflects the order of the genes on the chromosome and the distance between the genes on the same chromosome. These conclusions of Morgan and his collaborators are called the chromosome theory of heredity. The most important consequences of this theory are modern ideas about the gene as a functional unit of heredity, its divisibility and ability to interact with other genes.
The tasks illustrating the chromosome theory are quite complex and cumbersome to write down, therefore, in the examination papers of the Unified State Examination, assignments are given for inheritance linked to sex.
Sex genetics. Sex-linked inheritance. The chromosome sets of different sexes differ in the structure of the sex chromosomes. The male Y chromosome does not contain many of the alleles found on the X chromosome. The traits determined by the genes of the sex chromosomes are called sex-linked. The nature of inheritance depends on the distribution of chromosomes in meiosis. In heterogametic sexes, traits linked to the X chromosome and not having an allele on the Y chromosome appear even when the gene that determines the development of these traits is recessive. In humans, the Y chromosome is passed from father to sons, and the X chromosome to daughters. Children receive the second chromosome from their mother. It is always the X chromosome. If the mother carries a pathological recessive gene on one of the X chromosomes (for example, the gene for color blindness or hemophilia), but she herself is not sick, then she is a carrier. If this gene is passed on to sons, they may be sick with this disease, because there is no allele on the Y chromosome that suppresses the pathological gene. The sex of the organism is determined at the time of fertilization and depends on the chromosome set of the resulting zygote. In birds, females are heterogametic and males are homogametic.
An example of sex-linked inheritance. It is known that in humans there are several traits linked to the X chromosome. One of these signs is the absence of sweat glands. This is a recessive trait, if the X chromosome, which carries the gene that determines it, gets to the boy, then this trait will definitely appear in him. If you have read Patrick Suskind's famous novel The Perfume, then you will remember that it was about a baby who had no scent.
Consider an example of sex-linked inheritance. The mother has sweat glands, but she is a carrier of the recessive trait - Xp X, the father is healthy - XY. Mother's gametes - Xp, X. Father's gametes - X, Y.
From this marriage, children can be born with the following genotypes and phenotypes:
Genotype as an integral, historically established system. The term genotype was proposed in 1909 by the Danish geneticist Wilhelm Johansen. He also introduced the terms: gene, allele, phenotype, line, pure line, population.
Genotype is the totality of the genes of an organism. According to the latest data, a person has about 35 thousand genes.
The genotype, as a single functional system of the body, has developed in the process of evolution. A sign of the systemic nature of the genotype is gene interaction .
Allelic genes (more precisely, their products - proteins) can interact with each other:
– within the chromosomes– an example is complete and incomplete linkage of genes;
– on a pair of homologous chromosomes– examples are complete and incomplete dominance, independent expression of allelic genes.
Non-allelic genes can also interact with each other. An example of such an interaction can be the appearance of neoplasms when two outwardly identical forms are crossed. For example, the inheritance of the shape of the comb in chickens is determined by two genes - R and P: R - rose-shaped comb, P - pea-shaped comb.
F1 RrPp - the appearance of a walnut ridge in the presence of two dominant genes;
with the genotype ggrr, a leaf-shaped ridge appears.
EXAMPLES OF TASKS Part AA1. How many pairs of chromosomes are responsible for the inheritance of sex in dogs if their diploid set is 78?
3) thirty six
4) eighteen
A2. Linked inheritance patterns refer to genes located in
1) different non-homologous chromosomes
2) homologous chromosomes
3) in one chromosome
4) non-homologous chromosomes
A3. A colorblind man married a woman with normal vision, a carrier of the gene for colorblindness. A child with what genotype they can not have?
1) X d X 2) XX 3) X d X d 4) XY
A4. What is the number of gene linkage groups if it is known that the diploid set of chromosomes of an organism is 36?
1) 72 2) 36 3) 18 4) 9
A5. The frequency of crossing over between the K and C genes is 12%, between the B and C genes, 18%, and between the K and B genes, 24%. What is the likely order of genes on a chromosome if they are known to be linked.
1) K-S-B 2) K-B-S 3) S-B-K 4) B-K-S
A6. What will be the splitting in phenotype in the offspring obtained from crossing black (A) hairy (B) guinea pigs, heterozygous for two traits linked on the same chromosome?
1) 1: 1 2) 2: 1 3) 3: 1 4) 9: 3: 3: 1
A7. From the crossing of two gray rats heterozygous for two color traits, 16 individuals were obtained. What will be the ratio of offspring if it is known that gene C is the main color gene and in its presence gray, white and black individuals appear, and the second gene A affects the distribution of the pigment. In his presence, gray individuals appear.
1) 9 gray, 4 black, 3 white
2) 7 black, 7 black, 2 white
3) 3 black, 8 white, 5 gray
4) 9 gray, 3 black, 4 white
A8. The couple had a son with hemophilia. He grew up and decided to marry a healthy woman who did not carry the hemophilia gene. What are the possible phenotypes of future children of this married couple, if the gene is linked to the X chromosome?
1) all girls are healthy and not carriers, but boys with hemophilia
2) all the boys are healthy, and the girls are hemophilic
3) half of the girls are sick, the boys are healthy
4) all girls are carriers, boys are healthy
Part FROMC1. Make a forecast for the appearance of a color-blind grandson of a color-blind man and a healthy woman who does not carry the color blind gene, provided that all his sons marry healthy women who do not carry the color blind gene, and his daughters marry healthy men. Prove your answer by writing the crossover scheme.
3.6. Variability of traits in organisms: modification, mutation, combinative. Types of mutations and their causes. The value of variability in the life of organisms and in evolution. reaction rate
The main terms and concepts tested in the examination paper: twin method, genealogical method, gene mutations, genomic mutations, genotypic variability, the law of homologous series of hereditary variability, combinative variability, modification variability, mutations, non-hereditary variability, polyploidy, Rh factor, pedigree, Down syndrome, chromosomal mutations, cytogenetic method.
3.6.1. Variability, its types and biological significance
Variability- this is a general property of living systems associated with changes in the phenotype and genotype that occur under the influence of the external environment or as a result of changes in hereditary material. Distinguish between non-hereditary and hereditary variability.
Non-hereditary variability . Non-hereditary, or group (defined), or modification variability- these are changes in the phenotype under the influence of environmental conditions. Modification variability does not affect the genotype of individuals. The genotype, while remaining unchanged, determines the limits within which the phenotype can change. These limits, i.e. opportunities for the phenotypic manifestation of a trait are called reaction rate And inherited. The reaction norm sets the boundaries within which a particular feature can change. Different signs have a different reaction rate - wide or narrow. So, for example, such signs as blood type, eye color do not change. The shape of the mammalian eye changes insignificantly and has a narrow reaction rate. The milk yield of cows can vary over a fairly wide range depending on the conditions of the breed. Other quantitative characteristics may also have a wide reaction rate - growth, leaf size, number of grains per cob, etc. The wider the reaction rate, the more opportunities an individual has to adapt to environmental conditions. That is why there are more individuals with an average expression of a trait than individuals with its extreme expressions. This is well illustrated by such an example as the number of dwarfs and giants in humans. There are few of them, while there are thousands of times more people with a height in the range of 160-180 cm.
The phenotypic manifestations of a trait are influenced by the cumulative interaction of genes and environmental conditions. Modification changes are not inherited, but they do not necessarily have a group character and do not always manifest themselves in all individuals of a species under the same environmental conditions. Modifications ensure that the individual is adapted to these conditions.
hereditary variability (combinative, mutational, indeterminate).
Combination variability occurs during the sexual process as a result of new combinations of genes that occur during fertilization, crossing over, conjugation, i.e. in processes accompanied by recombinations (redistribution and new combinations) of genes. As a result of combinative variability, organisms arise that differ from their parents in genotypes and phenotypes. Some combinative changes can be detrimental to an individual. For the species, combinative changes are, in general, useful, because. lead to genotypic and phenotypic diversity. This contributes to the survival of species and their evolutionary progress.
Mutational variability associated with changes in the sequence of nucleotides in DNA molecules, deletions and insertions of large sections in DNA molecules, changes in the number of DNA molecules (chromosomes). Such changes are called mutations. Mutations are inherited.
Mutations include:
– genetic- causing changes in the sequence of DNA nucleotides in a particular gene, and therefore in the mRNA and protein encoded by this gene. Gene mutations are both dominant and recessive. They can lead to the appearance of signs that support or depress the vital activity of the organism;
– generative mutations affect germ cells and are transmitted during sexual reproduction;
– somatic mutations do not affect germ cells and are not inherited in animals, while in plants they are inherited during vegetative propagation;
– genomic mutations (polyploidy and heteroploidy) are associated with a change in the number of chromosomes in the cell karyotype;
– chromosomal mutations are associated with rearrangements in the structure of chromosomes, a change in the position of their sections resulting from breaks, loss of individual sections, etc.
The most common gene mutations, as a result of which there is a change, loss or insertion of DNA nucleotides in the gene. Mutant genes transmit different information to the site of protein synthesis, and this, in turn, leads to the synthesis of other proteins and the emergence of new traits. Mutations can occur under the influence of radiation, ultraviolet radiation, various chemical agents. Not all mutations are effective. Some of them are corrected during DNA repair. Phenotypically, mutations are manifested if they did not lead to the death of the organism. Most gene mutations are recessive. Of evolutionary importance are phenotypically manifested mutations that provided individuals with either advantages in the struggle for existence, or vice versa, which caused their death under the pressure of natural selection.
The mutation process increases the genetic diversity of populations, which creates the prerequisites for the evolutionary process.
The frequency of mutations can be increased artificially, which is used for scientific and practical purposes.
EXAMPLES OF TASKS Part BUTA1. Modification variability is understood as
1) phenotypic variability
2) genotypic variability
3) reaction rate
4) any changes in the feature
A2. Indicate the trait with the widest reaction rate
1) the shape of the wings of a swallow
2) the shape of an eagle's beak
3) hare molting time
4) the amount of wool in a sheep
A3. Specify the correct statement
1) environmental factors do not affect the genotype of an individual
2) it is not the phenotype that is inherited, but the ability to manifest it
3) modification changes are always inherited
4) modification changes are harmful
A4. Give an example of a genomic mutation
1) the occurrence of sickle cell anemia
2) the appearance of triploid potato forms
3) the creation of a tailless dog breed
4) the birth of an albino tiger
A5. With a change in the sequence of DNA nucleotides in a gene,
1) gene mutations
2) chromosomal mutations
3) genomic mutations
4) combinative rearrangements
A6. A sharp increase in the percentage of heterozygotes in a population of cockroaches can lead to:
1) an increase in the number of gene mutations
2) the formation of diploid gametes in a number of individuals
3) chromosomal rearrangements in some members of the population
4) change in ambient temperature
A7. The accelerated skin aging of rural residents compared to urban ones is an example
1) mutational variability
2) combination variability
3) gene mutations under the influence of ultraviolet radiation
4) modification variability
A8. The main cause of chromosomal mutation can be
1) replacement of a nucleotide in a gene
2) change in ambient temperature
3) violation of meiotic processes
4) insertion of a nucleotide into a gene
Part BIN 1. What examples illustrate modification variability
1) human tan
2) birthmark on the skin
3) the density of the coat of a rabbit of the same breed
4) increase in milk yield in cows
5) six-fingered in humans
6) hemophilia
IN 2. Specify events related to mutations
1) a multiple increase in the number of chromosomes
2) changing the undercoat of a hare in winter
3) amino acid replacement in a protein molecule
4) the appearance of an albino in the family
5) growth of the root system of a cactus
6) the formation of cysts in protozoa
VZ. Match the feature that characterizes variability with its type
C1. What are the ways to achieve an artificial increase in the frequency of mutations and why should this be done?
C2. Find errors in the given text. Fix them. Indicate the numbers of sentences in which errors were made. Explain them.
1. Modification variability is accompanied by genotypic changes. 2. Examples of modification are hair lightening after long exposure to the sun, increasing the milk yield of cows while improving feeding. 3. Information about modification changes is contained in genes. 4. All modification changes are inherited. 5. The manifestation of modification changes is influenced by environmental factors. 6. All signs of one organism are characterized by the same reaction rate, i.e. the limits of their variability.
3.7. The harmful effects of mutagens, alcohol, drugs, nicotine on the genetic apparatus of the cell. Protection of the environment from pollution by mutagens. Identification of sources of mutagens in the environment (indirectly) and assessment of the possible consequences of their influence on one's own body. Human hereditary diseases, their causes, prevention
The main terms and concepts tested in the examination paper: biochemical method, twin method, hemophilia, heteroploidy, color blindness, mutagens, mutagenesis, polyploidy.
3.7.1. Mutagens, mutagenesis
Mutagens- these are physical or chemical factors, the influence of which on the body can lead to a change in its hereditary characteristics. These factors include x-rays and gamma rays, radionuclides, heavy metal oxides, certain types of chemical fertilizers. Some mutations can be caused by viruses. Such common agents in modern society as alcohol, nicotine, drugs can also lead to genetic changes in generations. The rate and frequency of mutations depend on the intensity of the influence of these factors. An increase in the frequency of mutations leads to an increase in the number of individuals with congenital genetic anomalies. Mutations that affect germ cells are inherited. However, mutations that occur in somatic cells can lead to cancer. Currently, research is being carried out to identify mutagens in the environment and effective measures are being developed to neutralize them. Despite the fact that the frequency of mutations is relatively low, their accumulation in the human gene pool can lead to a sharp increase in the concentration of mutant genes and their manifestation. That is why it is necessary to know about mutagenic factors and take measures at the state level to combat them.
medical genetics - chapter anthropogenetics studying human hereditary diseases, their origin, diagnosis, treatment and prevention. The main means of collecting information about the patient is medical genetic counseling. It is carried out in relation to persons in whom hereditary diseases were observed among relatives. The goal is to predict the probability of having children with pathologies, or to exclude the occurrence of pathologies.
Stages of counseling:
- identification of the carrier of the pathogenic allele;
- calculation of the probability of the birth of sick children;
– communication of the results of the study to future parents, relatives.
Hereditary diseases transmitted to offspring:
- gene linked to the X chromosome - hemophilia, color blindness;
- gene linked to the Y-chromosome - hypertrichosis (hair growth of the auricle);
- gene autosomal: phenylketonuria, diabetes mellitus, polydactyly, Huntington's chorea, etc.;
- chromosomal, associated with chromosome mutations, for example, cat's cry syndrome;
- genomic - poly- and heteroploidy - a change in the number of chromosomes in the karyotype of an organism.
polyploidy - two or more fold increase in the number of haploid set of chromosomes in the cell. Occurs as a result of nondisjunction of chromosomes in meiosis, duplication of chromosomes without subsequent cell division, fusion of nuclei of somatic cells.
Heteroploidy (aneuploidy) - a change in the number of chromosomes characteristic of a given species as a result of their uneven divergence in meiosis. Manifested in the appearance of an extra chromosome ( trisomy on chromosome 21 leads to Down's disease) or the absence of a homologous chromosome in the karyotype ( monosomy). For example, the absence of a second X chromosome in women causes Turner syndrome, which manifests itself in physiological and mental disorders. Sometimes there is polysomy - the appearance of several extra chromosomes in the chromosome set.
Methods of human genetics. Genealogical - a method of compiling genealogies from various sources - stories, photographs, paintings. The signs of ancestors are clarified and the types of inheritance of signs are established.
Inheritance types: a) autosomal dominant, b) autosomal recessive, c) sex-linked inheritance.
The person for whom a pedigree is drawn up is called proband.
Gemini. A method for studying genetic patterns on twins. Twins are identical (monozygous, identical) and fraternal (dizygotic, non-identical).
cytogenetic. Microscopic study of human chromosomes. Allows you to identify gene and chromosomal mutations.
Biochemical. Based on biochemical analysis, it allows to identify a heterozygous carrier of the disease, for example, a carrier of the phenylketonuria gene can be identified by an increased concentration phenylalanine in blood.
Population genetic. Allows you to make a genetic characteristic of the population, to assess the degree of concentration of various alleles and the measure of their heterozygosity. For the analysis of large populations, the Hardy-Weinberg law is applied.
EXAMPLES OF TASKS Part FROMC1. Huntington's chorea is a severe disease of the nervous system, inherited as an autosomal trait (A).
Phenylketonuria - a disease that causes metabolic disorders, is determined by a recessive gene, is inherited according to the same type. The father is heterozygous for the gene of Huntington's chorea and does not suffer from phenylketonuria. The mother does not suffer from Huntington's chorea and does not carry the genes that determine the development of phenylketonuria. What are the possible genotypes and phenotypes of children from this marriage?
C2. A woman with a quarrelsome character married a man with a gentle character. From this marriage two daughters and a son were born (Elena, Lyudmila, Nikolai). Elena and Nikolai turned out to be an absurd character. Nikolai married a girl Nina with a gentle character. They had two sons, one of whom (Ivan) was a brawler, and the other a gentle man (Peter). Indicate the genotypes of all its members on the pedigree of this family.
3.8. Breeding, its tasks and practical significance. The teachings of N.I. Vavilov about the centers of diversity and origin of cultivated plants. The law of homologous series in hereditary variability. Methods for breeding new varieties of plants, animal breeds, strains of microorganisms. The value of genetics for selection. Biological Basis for Cultivation of Cultivated Plants and Domestic Animals
The main terms and concepts tested in the examination paper: heterosis, hybridization, law of homological series of hereditary variability, artificial selection, polyploidy, breed, selection, variety, centers of origin of cultivated plants, pure line, inbreeding.
3.8.1. Genetics and selection
Breeding is a science, a branch of practical activity aimed at creating new varieties of plants, animal breeds, strains of microorganisms with stable hereditary traits that are beneficial to humans. The theoretical basis of selection is genetics.
Selection tasks:
– qualitative improvement of the trait;
– increase in yield and productivity;
- increasing resistance to pests, diseases, climatic conditions.
selection methods. artificial selection - preservation of organisms necessary for a person and elimination, culling of others that do not meet the goals of the breeder.
The breeder sets a task, selects parent pairs, selects offspring, conducts a series of closely related and distant crosses, then selects in each subsequent generation. Artificial selection happens individual And massive.
Hybridization - the process of obtaining new genetic combinations in offspring to enhance or a new combination of valuable parental traits.
Closely related hybridization (inbreeding) used to draw clean lines. The disadvantage is the oppression of viability.
distant hybridization shifts the reaction rate in the direction of strengthening the trait, the appearance of hybrid power (heterosis). The disadvantage is the non-crossability of the resulting hybrids.
Overcoming the sterility of interspecific hybrids. Polyploidy. G.D. Karpechenko in 1924 treated a sterile hybrid of cabbage and radish with colchicine. Colchicine caused nondisjunction of chromosomes of the hybrid during gametogenesis. The fusion of diploid gametes led to the production of a polyploid hybrid of cabbage and radish (kapredki). G. Karpechenko's experiment can be illustrated by the following scheme.
1. Before the action of colchicine
2. After the action of colchicine and artificial duplication of chromosomes:
3.8.2. Methods of work I.V. Michurin
I. V. Michurin, a domestic breeder, bred about 300 varieties of fruit trees that combined the qualities of southern fruits and the unpretentiousness of northern plants.
Basic working methods:
– distant hybridization of geographically distant varieties;
– strict individual selection;
- "education" of hybrids by harsh growing conditions;
- “dominance management” using the mentor method - grafting a hybrid to an adult plant that transfers its qualities to the bred variety.
Overcoming non-crossing in distant hybridization:
- the method of preliminary approach - grafting a cutting of one species (mountain ash) was grafted onto the crown of a pear. A few years later, rowan flowers were pollinated by pear pollen. So a hybrid of mountain ash and pear was obtained;
– mediator method – 2-step hybridization. The almond was crossed with the semi-cultivated David peach, and then the resulting hybrid was crossed with a cultivar. Got "Northern Peach";
- Pollination by mixed pollen (own and someone else's). An example is the production of cerapadus, a hybrid of cherry and bird cherry.
3.8.3. Centers of origin of cultivated plants
The largest Russian scientist - geneticist N.I. Vavilov made a huge contribution to plant breeding. He found that all cultivated plants grown today in different regions of the world have certain geographical
centers of origin. These centers are located in tropical and subtropical zones, i.e., where cultivated agriculture originated. N.I. Vavilov singled out 8 such centers, i.e. 8 independent areas of introduction to the culture of various plants.
The variety of cultivated plants in the centers of their origin is usually represented by a huge number of botanical varieties and many hereditary variants.
The law of homologous series of hereditary variability.
1. Species and genera that are genetically close are characterized by similar series of hereditary variability with such regularity that, knowing the number of forms within one species, one can foresee the occurrence of parallel forms in other species and genera. The closer species and genera are genetically located in the general system, the more complete is the similarity in the series of their variability.
2. Whole families of plants, in general, are characterized by a certain cycle of variability, passing through all the genera and species that make up the family.
This law was introduced by N.I. Vavilov based on the study of a huge number of genetically related species and genera. The closer the relationship between these taxonomic groups and within them, the greater the genetic similarity they have. Comparing different types and genera of cereals, N.I. Vavilov and his collaborators found that all cereals have similar characteristics, such as branching and density of the ear, pubescence of scales, etc. Knowing this, N.I. Vavilov suggested that such groups have similar hereditary variability: "if you can find a awnless form of wheat, you can also find a awnless form of rye." Knowing the possible nature of changes in representatives of a certain species, genus, family, a breeder can purposefully search, create new forms and either weed out or save individuals with the necessary genetic changes.
EXAMPLES OF TASKSPart AA1. The domestication of animals and plants is based on
1) artificial selection 3) domestication
2) natural selection 4) methodical selection
A2. In the Mediterranean center of cultivated plants,
1) rice, mulberry 3) potatoes, tomatoes
2) breadfruit, peanuts 4) cabbage, olive, swede
A3. An example of genomic variation is
1) sickle cell anemia
2) polyploid form of potato
3) albinism
3) color blindness
A4. Roses that are similar in appearance and genetically, artificially
bred by breeders form
1) breed 2) variety 3) species 4) variety
A5. The benefits of heterosis are
1) the appearance of clean lines
2) overcoming the non-crossing of hybrids
3) increase in productivity
4) increasing the fertility of hybrids
A6. As a result of polyploidy
1) fertility occurs in interspecific hybrids
2) fertility disappears in interspecific hybrids
3) a clean line is maintained
4) the viability of hybrids is inhibited
A7. Inbreeding in breeding is used for
1) strengthening hybrid properties
2) drawing clean lines
3) increase the fertility of offspring
4) increasing the heterozygosity of organisms
A8. The law of homologous series of hereditary variability allowed breeders with greater reliability
1) display polyploid forms
2) overcome the non-crossing of different species
3) increase the number of random mutations
4) predict the acquisition of the desired traits in plants
A9. Inbreeding increases
1) population heterozygosity
2) frequency of dominant mutations
3) homozygosity of the population
4) frequency of recessive mutations
Part BIN 1. Establish a correspondence between the features of the selection method and its name.
C1. Compare the results from the use of such selection methods as inbreeding, polyploidy. Explain these results.
3.9. Biotechnology, cell and genetic engineering, cloning. The role of cell theory in the formation and development of biotechnology. The importance of biotechnology for the development of breeding, agriculture, the microbiological industry, and the preservation of the planet's gene pool. Ethical aspects of the development of some research in biotechnology (human cloning, directed changes in the genome)
The main terms and concepts tested in the examination paper: biotechnology, genetic engineering, cell engineering.
3.9.1. Cellular and genetic engineering. Biotechnology
Cell engineering is a direction in science and breeding practice that studies the methods of hybridization of somatic cells belonging to different species, the possibility of cloning tissues or entire organisms from individual cells.
One of the common methods of plant breeding is the haploid method - obtaining full-fledged haploid plants from sperm or eggs.
Hybrid cells have been obtained that combine the properties of blood lymphocytes and tumor, actively proliferating cells. This allows you to quickly and in the right quantities to obtain antibodies.
tissue culture - used to obtain in the laboratory plant or animal tissues, and sometimes whole organisms. In crop production, it is used to accelerate the production of pure diploid lines after treatment of the original forms with colchicine.
Genetic Engineering- artificial, purposeful change in the genotype of microorganisms in order to obtain cultures with predetermined properties.
Main Method- isolation of the necessary genes, their cloning and introduction into a new genetic environment. The method includes the following work steps:
- isolation of the gene, its combination with the DNA molecule of the cell, which can reproduce the donor gene in another cell (inclusion in the plasmid);
– introduction of a plasmid into the genome of a bacterial cell – a recipient;
– selection of necessary bacterial cells for practical use;
– research in the field of genetic engineering extends not only to microorganisms, but also to humans. They are especially relevant in the treatment of diseases associated with disorders in the immune system, in the blood coagulation system, in oncology.
Cloning . From a biological point of view, cloning is the vegetative reproduction of plants and animals, the offspring of which carries hereditary information identical to the parent. In nature, plants, fungi, and protozoa are cloned; organisms that reproduce vegetatively. In recent decades, this term has been used when the nuclei of one organism are transplanted into the egg of another. An example of such cloning was the famous sheep Dolly, obtained in England in 1997.
Biotechnology– the process of using living organisms and biological processes in the production of medicines, fertilizers, biological plant protection products; for biological wastewater treatment, for biological extraction of valuable metals from sea water, etc.
The inclusion in the genome of E. coli of the gene responsible for the formation of insulin in humans made it possible to establish the industrial production of this hormone.
Agriculture has succeeded in genetically modifying dozens of food and fodder crops. In animal husbandry, the use of biotechnologically produced growth hormone has increased milk yields;
using a genetically modified virus to create a vaccine against herpes in pigs. With the help of newly synthesized genes introduced into bacteria, a number of the most important biologically active substances are obtained, in particular hormones and interferon. Their production constituted an important branch of biotechnology.
With the development of genetic and cell engineering, there is more and more concern in society about the possible manipulation of genetic material. Some concerns are theoretically justified. For example, it is impossible to exclude the transplantation of genes that increase resistance to antibiotics of some bacteria, the creation of new forms of food products, but these works are controlled by states and society. In any case, the danger from disease, malnutrition and other shocks is much higher than from genetic research.
Prospects for Genetic Engineering and Biotechnology:
- the creation of organisms useful to humans;
– obtaining new drugs;
– correction and correction of genetic pathologies.
EXAMPLES OF TASKS Part AA1. The production of drugs, hormones and other biological substances is engaged in such a direction as
1) genetic engineering
2) biotech production
3) agricultural industry
4) agronomy
A2. When would tissue culture be the most useful method?
1) upon receipt of a hybrid of apple and pear
2) when breeding pure lines of smooth-seed peas
3) if necessary, transplant the skin to a person with a burn
4) upon receipt of polyploid forms of cabbage and radish
A3. In order to artificially obtain human insulin by genetic engineering methods on an industrial scale, it is necessary
1) introduce a gene responsible for the synthesis of insulin into bacteria that will begin to synthesize human insulin
2) inject bacterial insulin into the human body
3) artificially synthesize insulin in a biochemical laboratory
4) grow a cell culture of the human pancreas responsible for the synthesis of insulin.
Part FROMC1. Why are many in society afraid of transgenic products?
organism biological system
In biology, an organism is considered as an independently existing unit of the world, the functioning of which is possible only with constant interaction with its external environment and self-renewal as a result of such interaction.
The main function of the body is metabolism (metabolism), which is ensured by simultaneously and continuously occurring processes in all organs and tissues - assimilation and dissimilation.
Assimilation (anabolism) is reduced to the formation of substances entering the body from outside and the accumulation of new chemical compounds that go to the formation of various tissues (body weight) and the creation of the energy potential necessary for the implementation of life, including movements.
Dissimilation (catabolism) is the breakdown of chemicals into the body, the destruction of old, dead or damaged tissue elements of the body, as well as the release of energy from substances accumulated in the process of assimilation.
Metabolism is associated with such body functions as growth, development, reproduction, nutrition, digestion, respiration and excretion of waste products, movement, reactions to changes in the external environment, etc.
The influence of the environment on the organism is diverse, which is not only a supplier of vital substances for it, but also a source of disturbing influences (irritants). Constant fluctuations in external conditions stimulate appropriate adaptive reactions in the body, which prevent the possible occurrence of deviations in its internal environment (blood, lymph, tissue fluid) and most cellular structures.
In the process of evolution, in the formation of the relationship of the organism with the external environment, it developed the most important property to maintain the constancy of the composition of the internal environment - homeostasis (from the Greek "homoyos" - the same, "stasis" - state). The expression of homeostasis is the presence of a number of biological constants - stable quantitative indicators that characterize the normal state of the body. These include body temperature, the content of proteins, sugar, sodium and potassium ions in the blood and tissue fluid, etc. The constants determine the physiological boundaries of homeostasis, therefore, with a long stay of the body in conditions that differ significantly from those to which it is adapted, homeostasis is disturbed and there may be shifts incompatible with normal life.
However, the adaptive mechanisms of the body are not limited to maintaining the homeostatic state, maintaining the constancy of regulated functions. For example, with various kinds of physical activity, the direction of regulation is focused on providing optimal conditions for the functioning of the body due to increased requirements (increased heart rate, respiratory movements, activation of metabolic processes, etc.).
Modern science considers the body as a self-regulating biological system in which all cells, tissues, organs are in close relationship and interaction, forming a single whole with high functional efficiency. More I.P. Pavlov emphasized "a person is ... a system that is self-regulating to the highest degree, supporting itself, restoring, correcting and even improving."
The relationship of functions and processes is provided by two regulatory mechanisms - humoral and nervous, which were dominant in the process of biological adaptation in the animal world, and then gradually transformed into regulators of body functions.
The humoral mechanism (from the Latin “humor” - liquid) of regulation is carried out due to the chemicals that are contained in the fluids circulating in the body (blood, lymph, tissue fluid). The most important of them are hormones(from the Greek "hormon" - moving), which are secreted by the endocrine glands. Once in the bloodstream, they reach all organs and tissues, regardless of whether they participate in the regulation of functions or not. Only the selective ratio of tissues to a particular substance determines the inclusion of the hormone in the regulation process. Hormones move at the speed of blood flow without a specific "addressee". Between various chemical regulators, especially hormones, the principle of self-regulation is clearly manifested. For example, if the amount of insulin (pancreatic hormone) in the blood becomes excessive, this serves as a trigger for increased production of adrenaline (hormone of the adrenal medulla). The dynamic balance of the level of concentration of these hormones ensures optimal blood sugar levels.
The nervous mechanism of regulation is carried out through nerve impulses that travel along certain nerve fibers to strictly defined organs or tissues of the body. Nervous regulation is more perfect than humoral, because, firstly, the propagation of nerve impulses is faster (from 0.5 to 120 m/s) and, secondly, they are targeted, i.e. along neural pathways, impulses go to specific cells or groups of cells.
The main nervous mechanism for regulating functions is the reflex response of tissues or organs to irritation coming from the external and internal environment. It is realized along a reflex arc - the path along which excitation occurs from receptors to executive organs (muscles, glands) that respond to irritation. There are two types of reflexes: unconditioned or congenital and conditioned or acquired. Nervous regulation of body functions consists of the most complex relationships between these two types of reflexes.
Nervous and humoral regulation of functions are closely interrelated and form a single neurohumoral regulation. For example, the transmitter of nervous excitation is a humoral (chemical) component - a mediator, and the activity of many endocrine glands is stimulated by nerve impulses. The ratio of nervous and humoral links in the mechanism of control of body functions boils down to the fact that the predominance of the nervous component takes place if the controlled function is more associated with environmental stimuli, and the role of the humoral mechanism increases as these connections weaken.
In the process of motor activity, muscles contract, the heart changes its work, the glands secrete hormones into the blood, which, in turn, have an intensifying or weakening effect on the same muscles, heart and other organs. In other words, the reflex reaction is accompanied by humoral shifts, and the humoral shift is accompanied by a change in reflex regulation.
The functioning of the nervous system and the chemical interaction of cells and organs provide the most important ability of the body - self-regulation of physiological functions, leading to the automatic maintenance of the necessary conditions for the body to exist. Any shift in the external or internal environment of the organism causes its activity, aimed at restoring the disturbed constancy of the conditions of its vital activity, i.e. restoration of homeostasis. The more developed the organism, the more perfect and stable the homeostasis.
The essence of self-regulation is aimed at achieving a specific result in the management of organs and the processes of their functioning in the body based on information about this, which circulates in direct and feedback channels in a closed cycle, for example, thermoregulation, pain, etc.). The function of communication channels can be performed by receptors, nerve cells, fluids circulating in the body, etc. Self-regulation is carried out according to certain patterns. There are a number of principles of self-regulation. The principle of non-equilibrium expresses the ability of a living organism to maintain its homeostasis on the basis of maintaining a dynamic non-equilibrium, asymmetric state relative to the environment. At the same time, the organism as a biological system not only counteracts unfavorable influences and facilitates the action of positive influences on it, but in the absence of both, it can show spontaneous activity, reflecting the enormous amount of activity to create basic structures. Consolidation of the results of spontaneous activity in newly emerging structures forms the basis for developmental phenomena. The principle of a closed control loop is that in a living system, information about the reaction to an incoming stimulus is analyzed in a certain way and, if necessary, corrected. Information circulates in a closed loop with direct and feedback until the desired result is achieved. An example is the regulation of skeletal muscle function. From the central nervous system (CNS) the muscle receives stimulation through direct communication channels, the muscle responds to it with a contraction (or tension). Information about the degree of muscle contraction through feedback channels enters the central nervous system, where the result is compared and evaluated relative to the proper one. If they do not match, a new corrective impulse is sent from the central nervous system to the muscle. Information will circulate in a closed loop until the muscle response reaches the desired level. The principle of forecasting is that a biological system, as it were, determines its behavior (reactions, processes) in the future based on an assessment of the probability of repeating past experience. As a result of such a forecast, the basis of preventive regulation is formed in it as an adjustment to the expected event, the meeting with which optimizes the mechanisms of corrective activity. For example, the predictive signaling function of the conditioned reflex; the use of elements of previously formed motor actions in the development of new ones.
TOPIC 2. SOCIO-BIOLOGICAL FOUNDATIONS OF PHYSICAL CULTURE
Introduction
1. Organism as a biological system.
2. Anatomical - morphological features of the body.
3. Skeletal system and its functions.
4. The muscular system and its functions.
5. Organs of digestion and excretion.
6. Physiological systems of the body.
7. Motor activity of a person and the relationship of physical and mental activity.
8. Means of physical culture, providing resistance to mental and physical performance.
9.Functional indicators of the fitness of the body at rest and when performing extremely hard work.
10. Metabolism and energy.
11. Control questions.
Introduction
Socio-biological foundations of physical culture are the principles of interaction of social and biological patterns in the process of mastering the values of physical culture by a person.
Man obeys the biological laws inherent in all living beings. However, it differs from representatives of the animal world not only in structure, but in developed thinking, intellect, speech, features of social and living conditions and social relationships. Labor and the influence of the social environment in the process of human development have influenced the biological characteristics of the organism of modern man and his environment. An organism is a well-coordinated single self-regulating and self-developing biological system, the functional activity of which is determined by the interaction of mental, motor and vegetative reactions to environmental influences, which can be both beneficial and detrimental to health. A distinctive feature of a person is a conscious and active influence on external natural and social conditions that determine the state of people's health, their performance, life expectancy and fertility (reproductivity). Without knowledge about the structure of the human body, about the patterns of functioning of individual organs and systems of the body, about the features of the flow of complex processes of its life, it is impossible to organize the process of forming a healthy lifestyle and physical training of the population, including young students. Achievements of biomedical sciences underlie the pedagogical principles and methods of the educational and training process, the theory and methodology of physical education and sports training.
The organism as a biological system
In biology, an organism is considered as an independently existing unit of the world, the functioning of which is possible only with constant interaction with its external environment.
Each born person inherits from his parents congenital, genetically determined traits and characteristics that largely determine individual development in the process of his later life. Once born in an autonomous mode, the child grows rapidly, the mass, length and surface area of his body increase. Human growth continues until about 20 years of age. Moreover, in girls, the greatest intensity of growth is observed in the period from 10 to 13, and in boys from 12 to 16 years. An increase in body weight occurs almost in parallel with an increase in its length and stabilizes by the age of 20-25.
It should be noted that over the past 100-150 years in a number of countries there has been an early morphofunctional development of the body in children and adolescents. This phenomenon is called acceleration (Latin accelera-tio- acceleration).
The elderly (61-74 years) and senile (75 years and more) are characterized by physiological processes of restructuring: a decrease in the active capabilities of the body and its systems - immune, nervous, circulatory, etc. A healthy lifestyle, active motor activity in the process of life significantly slow down the process aging.
The vital activity of the organism is based on the process of automatic maintenance of vital factors at the required level, any deviation from which leads to the immediate mobilization of mechanisms that restore this level.
3.2. Reproduction of organisms, its significance. Methods of reproduction, similarities and differences between sexual and asexual reproduction. The use of sexual and asexual reproduction in human practice. The role of meiosis and fertilization in ensuring the constancy of the number of chromosomes in generations. The use of artificial insemination in plants and animals.
3.3. Ontogeny and its inherent regularities. Specialization of cells, formation of tissues, organs. Embryonic and postembryonic development of organisms. Life cycles and alternation of generations. Causes of disruption in the development of organisms.
3.5. Patterns of heredity, their cytological basis. Mono- and dihybrid crossing. Patterns of inheritance established by G. Mendel. Linked inheritance of traits, violation of the linkage of genes. Laws of T. Morgan. Chromosomal theory of heredity. Sex genetics. Inheritance of sex-linked traits. The genotype as an integral system. Development of knowledge about the genotype. The human genome. Interaction of genes. Solution of genetic problems. Drawing up cross-breeding schemes. G. Mendel's laws and their cytological foundations.
3.6. Variability of traits in organisms: modification, mutation, combinative. Types of mutations and their causes. The value of variability in the life of organisms and in evolution. reaction rate.
3.6.1. Variability, its types and biological significance.
3.7. The harmful effects of mutagens, alcohol, drugs, nicotine on the genetic apparatus of the cell. Protection of the environment from pollution by mutagens. Identification of sources of mutagens in the environment (indirectly) and assessment of the possible consequences of their influence on one's own body. Human hereditary diseases, their causes, prevention.
3.7.1. Mutagens, mutagenesis.
3.8. Breeding, its tasks and practical significance. The teachings of N.I. Vavilov about the centers of diversity and origin of cultivated plants. The law of homologous series in hereditary variability. Methods for breeding new varieties of plants, animal breeds, strains of microorganisms. The value of genetics for selection. Biological bases for growing cultivated plants and domestic animals.
3.8.1. Genetics and selection.
3.8.2. Methods of work I.V. Michurin.
3.8.3. Centers of origin of cultivated plants.
3.9. Biotechnology, cell and genetic engineering, cloning. The role of cell theory in the formation and development of biotechnology. The importance of biotechnology for the development of breeding, agriculture, the microbiological industry, and the preservation of the planet's gene pool. Ethical aspects of the development of some research in biotechnology (human cloning, directed changes in the genome).
3.9.1. Cellular and genetic engineering. Biotechnology.
Diversity of organisms: unicellular and multicellular; autotrophs, heterotrophs.
Unicellular and multicellular organisms
The extraordinary diversity of living beings on the planet forces us to find different criteria for their classification. So, they are classified as cellular and non-cellular forms of life, since cells are the structural unit of almost all known organisms - plants, animals, fungi and bacteria, while viruses are non-cellular forms.
Depending on the number of cells that make up the body, and the degree of their interaction, single-celled, colonial and multicellular organisms are distinguished. Despite the fact that all cells are morphologically similar and capable of performing the usual functions of a cell (metabolism, maintaining homeostasis, development, etc.), the cells of unicellular organisms perform the functions of an integral organism. Cell division in unicellular organisms entails an increase in the number of individuals, and there are no multicellular stages in their life cycle. In general, unicellular organisms have the same cellular and organismal levels of organization. The vast majority of bacteria, part of animals (protozoa), plants (some algae) and fungi are unicellular. Some taxonomists even propose to distinguish unicellular organisms into a special kingdom - protists.
Colonial called organisms in which, in the process of asexual reproduction, the daughter individuals remain connected to the mother organism, forming a more or less complex association - a colony. In addition to colonies of multicellular organisms, such as coral polyps, there are also colonies of unicellular organisms, in particular pandorina and eudorina algae. Colonial organisms, apparently, were an intermediate link in the process of the emergence of multicellular organisms.
Multicellular organisms, without a doubt, have a higher level of organization than unicellular, since their body is formed by many cells. Unlike colonial cells, which can also have more than one cell, in multicellular organisms, cells specialize in performing various functions, which is also reflected in their structure. The price for this specialization is the loss of their cells' ability to exist independently, and often to reproduce their own kind. The division of a single cell leads to the growth of a multicellular organism, but not to its reproduction. The ontogeny of multicellular organisms is characterized by the process of fragmentation of a fertilized egg into many blastomere cells, from which an organism with differentiated tissues and organs is subsequently formed. Multicellular organisms are generally larger than unicellular organisms. An increase in the size of the body in relation to their surface contributed to the complication and improvement of metabolic processes, the formation of the internal environment and, ultimately, provided them with greater resistance to environmental influences (homeostasis). Thus, multicellular organisms have a number of advantages in organization compared to unicellular organisms and represent a qualitative leap in the evolutionary process. Few bacteria are multicellular, most plants, animals and fungi.
Autotrophs and heterotrophs
According to the way of nutrition, all organisms are divided into autotrophs and heterotrophs. Autotrophs are capable of independently synthesizing organic substances from inorganic substances, while heterotrophs use exclusively ready-made organic substances.
Some autotrophs can use light energy for the synthesis of organic compounds - such organisms are called photoautotrophs, they are able to carry out photosynthesis. Plants and some bacteria are photo-autotrophs. They are closely adjacent to chemoautotrophs, which extract energy by oxidizing inorganic compounds in the process of chemosynthesis - these are some bacteria.
Saprotrophs called heterotrophic organisms that feed on organic residues. They play an important role in the cycle of substances in nature, since they ensure the completion of the existence of organic substances in nature, decomposing them to inorganic ones. Thus, saprotrophs participate in the processes of soil formation, water purification, etc. Many fungi and bacteria, as well as some plants and animals, belong to saprotrophs.
Viruses are non-cellular life forms
Characterization of viruses
Along with the cellular form of life, there are also its non-cellular forms - viruses, viroids and prions. Viruses (from Latin vira - poison) are the smallest living objects that are incapable of showing any signs of life outside the cells. The fact of their existence was proven back in 1892 by the Russian scientist D.I. Ivanovsky, who established that the disease of tobacco plants - the so-called tobacco mosaic - is caused by an unusual pathogen that passes through bacterial filters (Fig. 3.1), however, only in 1917 F d "Errel isolated the first virus - a bacteriophage. Viruses are studied by the science of virology (from Latin vira - poison and Greek logos - word, science).
In our time, about 1000 viruses are already known, which are classified according to the objects of damage, shape and other features, but the most common is the classification according to the chemical composition and structure of viruses.
Unlike cellular organisms, viruses consist only of organic substances - mainly nucleic acids and protein, but some viruses also contain lipids and carbohydrates.
All viruses are conditionally divided into simple and complex. Simple viruses consist of a nucleic acid and a protein shell - a capsid. The capsid is not monolithic, it is assembled from protein subunits - capsomeres. In complex viruses, the capsid is covered with a lipoprotein membrane - a supercapsid, which also includes glycoproteins and non-structural enzyme proteins. Bacterial viruses have the most complex structure - bacteriophages (from the Greek bacterion - stick and phagos - eater), in which the head and process, or "tail", are isolated. The head of a bacteriophage is formed by a protein capsid and a nucleic acid enclosed in it. In the tail, a protein sheath and a hollow rod hidden inside are distinguished. At the bottom of the rod there is a special plate with spikes and threads responsible for the interaction of the bacteriophage with the cell surface.
Unlike cellular life forms, which have both DNA and RNA, viruses contain only one type of nucleic acid (either DNA or RNA), so they are divided into DNA viruses, smallpox, herpes simplex, adenoviruses, some hepatitis viruses, and bacteriophages) and RNA-containing viruses (tobacco mosaic viruses, HIV, encephalitis, measles, rubella, rabies, influenza, other hepatitis viruses, bacteriophages, etc.). In some viruses, DNA can be represented by a single-stranded molecule, and RNA can be double-stranded.
Since viruses are devoid of organelles of movement, infection occurs by direct contact of the virus with the cell. It mainly occurs by airborne droplets (flu), through the digestive system (hepatitis), blood (HIV) or a carrier (encephalitis virus).
Viruses can enter the cell directly by accident, with fluid absorbed by pinocytosis, but more often their penetration is preceded by contact with the host cell membrane, as a result of which the nucleic acid of the virus or the entire viral particle is in the cytoplasm. Most viruses do not penetrate into any cell of the host organism, but into a strictly defined one, for example, hepatitis viruses infect liver cells, and influenza viruses infect cells of the mucous membrane of the upper respiratory tract, since they are able to interact with specific receptor proteins on the surface of the cell membrane - host, which are absent in other cells.
Due to the fact that the cells of plants, bacteria and fungi have strong cell walls, the viruses that infect these organisms have developed appropriate adaptations for penetration. Thus, after interacting with the surface of the host cell, bacteriophages “pierce” it with their rod and introduce nucleic acid into the cytoplasm of the host cell (Fig. 3.2). In fungi, infection occurs mainly when the cell walls are damaged; in plants, both the aforementioned path and the penetration of the virus through plasmodesmata are possible.
After penetration into the cell, the “undressing” of the virus occurs, that is, the loss of the capsid. Further events depend on the nature of the nucleic acid of the virus: DNA-containing viruses insert their DNA into the genome of the host cell (bacteriophages), and on RNA, either DNA is first synthesized, which is then integrated into the genome of the host cell (HIV), or it can directly protein synthesis occurs (influenza virus). Reproduction of the nucleic acid of the virus and the synthesis of capsid proteins using the protein-synthesizing apparatus of the cell are essential components of a viral infection, after which the self-assembly of viral particles and their release from the cell occur. Virus particles in some cases leave the cell, gradually budding from it, and in other cases, a microexplosion occurs, accompanied by cell death.
Viruses not only inhibit the synthesis of their own macromolecules in the cell, but are also capable of causing damage to cellular structures, especially during mass exit from the cell. This leads, for example, to the mass death of industrial cultures of lactic acid bacteria in the event of damage by some bacteriophages, impaired immunity due to the destruction of HIV T4-lymphocytes, which are one of the central links of the body's defenses, to numerous hemorrhages and death of a person as a result of infection with the Ebola virus, to cell degeneration and the formation of a cancerous tumor, etc.
Despite the fact that viruses that have entered a cell often quickly suppress its repair systems and cause death, another scenario is also likely - the activation of the body's defenses, which is associated with the synthesis of antiviral proteins, such as interferon and immunoglobulins. In this case, the reproduction of the virus is interrupted, new viral particles are not formed, and the remnants of the virus are removed from the cell.
Viruses cause numerous diseases in humans, animals and plants. In plants, this is a mosaic of tobacco and tulips, in humans - influenza, rubella, measles, AIDS, etc. In the history of mankind, smallpox viruses, "Spanish flu", and now HIV have claimed the lives of hundreds of millions of people. However, infection can also increase the body's resistance to various pathogens (immunity), and thus contribute to their evolutionary progress. In addition, viruses are able to “grab” parts of the host cell’s genetic information and transfer them to the next victim, thereby providing the so-called horizontal gene transfer, the formation of mutations and, in the end, the supply of material for the evolutionary process.
In our time, viruses are widely used in the study of the structure and functions of the genetic apparatus, as well as the principles and mechanisms for the implementation of hereditary information, they are used as a tool for genetic engineering and biological control of pathogens of certain diseases of plants, fungi, animals and humans.
AIDS disease and HIV infection
HIV (human immunodeficiency virus) was discovered only in the early 1980s, but the spread of the disease it causes and the impossibility of a cure at this stage in the development of medicine make it necessary to pay increased attention to it. In 2008, F. Barre-Sinoussi and L. Montagnier were awarded the Nobel Prize in Physiology or Medicine for their research on HIV.
HIV is a complex RNA-containing virus that mainly infects T4 lymphocytes, which coordinate the work of the entire immune system (Fig. 3.3). On the RNA of the virus, using the enzyme RNA-dependent DNA polymerase (reverse transcriptase), DNA is synthesized, which is integrated into the genome of the host cell, turns into a provirus and “hidden” for an indefinite time. Subsequently, reading information about viral RNA and proteins begins from this DNA section, which are assembled into viral particles and leave it almost simultaneously, dooming them to death. Viral particles infect all new cells and lead to a decrease in immunity.
HIV infection has several stages, while for a long period a person can be a carrier of the disease and infect other people, but no matter how long this period lasts, the last stage still occurs, which is called acquired immunodeficiency syndrome, or AIDS.
The disease is characterized by a decrease, and then a complete loss of the body's immunity to all pathogens. Signs of AIDS are chronic damage to the mucous membranes of the oral cavity and skin by pathogens of viral and fungal diseases (herpes, yeast fungi, etc.), severe pneumonia and other AIDS-associated diseases.
HIV is transmitted sexually, through blood and other bodily fluids, but is not transmitted through handshakes and household items. At first, in our country, HIV infection was more often associated with indiscriminate sexual contacts, especially homosexual, injection drug addiction, and transfusion of contaminated blood, but now the epidemic has gone beyond the risk groups and is rapidly spreading to other categories of the population.
The main means of preventing the spread of HIV infection are the use of condoms, legibility in sexual relations and avoidance of drug use.
Measures to prevent the spread of viral diseases
The main means of preventing viral diseases in humans is to wear gauze bandages when in contact with sick respiratory diseases, washing hands, vegetables and fruits, pickling habitats of carriers of viral diseases, vaccination against tick-borne encephalitis, sterilization of medical instruments in medical institutions, etc. To avoid infection HIV should also give up the use of alcohol, drugs, have a single sexual partner, use personal protective equipment during sexual intercourse, etc.
Viroids
Viroids (from Latin virus - poison and Greek eidos - form, species) are the smallest pathogens of plant diseases, which include only low molecular weight RNA.
Their nucleic acid probably does not encode their own proteins, but is only reproduced in the cells of the host plant using its enzyme systems. Often, it can also cut the DNA of the host cell into several pieces, thereby dooming the cell and the plant as a whole to death. So, a few years ago, viroids caused the death of millions of coconut trees in the Philippines.
prions
Prions (abbr. English proteinaceous infectious and -on) are small infectious agents of protein nature, having the form of a thread or a crystal.
Proteins of the same composition are present in a normal cell, but prions have a special tertiary structure. Getting into the body with food, they help the corresponding "normal" proteins to acquire the structure characteristic of the prions themselves, which leads to the accumulation of "abnormal" proteins and a deficiency of normal ones. Naturally, this causes disturbances in the functions of tissues and organs, especially the central nervous system, and the development of currently incurable diseases: “mad cow disease”, Creutzfeldt-Jakob disease, kuru, etc.
3.2. Reproduction of organisms, its significance. Methods of reproduction, similarities and differences between sexual and asexual reproduction. The use of sexual and asexual reproduction in human practice. The role of meiosis and fertilization in ensuring the constancy of the number of chromosomes in generations. The use of artificial insemination in plants and animals.
Reproduction of organisms, its significance
The ability of organisms to reproduce their own kind is one of the fundamental properties of living things. Despite the fact that life as a whole is continuous, the life span of a single individual is finite, therefore, the transfer of hereditary information from one generation to the next during reproduction ensures the survival of this species of organisms over long periods of time. Thus, reproduction ensures the continuity and succession of life.
A prerequisite for reproduction is to obtain a larger number of offspring than parental individuals, since not all offspring will be able to live to the stage of development at which they themselves can produce offspring, since they can be destroyed by predators, die from diseases and natural disasters, such as fires, floods, etc.
Methods of reproduction, similarities and differences between sexual and asexual reproduction
In nature, there are two main methods of reproduction - asexual and sexual.
Asexual reproduction is a method of reproduction in which neither the formation nor the fusion of specialized germ cells - gametes occurs, only one parent organism takes part in it. Asexual reproduction is based on mitotic cell division.
Depending on how many cells of the mother's body give rise to a new individual, asexual reproduction is divided into actually asexual and vegetative. With proper asexual reproduction, the daughter individual develops from a single cell of the mother's organism, and with vegetative reproduction, from a group of cells or an entire organ.
In nature, there are four main types of proper asexual reproduction: binary fission, multiple fission, sporulation and simple budding.
Binary fission is essentially a simple mitotic division of a unicellular maternal organism, in which the nucleus first divides, and then the cytoplasm. It is characteristic of various representatives of the plant and animal kingdoms, for example, Proteus amoeba and ciliates-shoes.
Multiple division, or schizogony, is preceded by repeated division of the nucleus, after which the cytoplasm is divided into the appropriate number of fragments. This type of asexual reproduction is found in unicellular animals - sporozoans, for example, in malarial plasmodium.
In many plants and fungi, in the life cycle, the formation of spores occurs - single-celled specialized formations containing a supply of nutrients and covered with a dense protective shell. Spores are dispersed by wind and water, and in the presence of favorable conditions germinate, giving rise to a new multicellular organism.
A characteristic example of budding as a kind of asexual reproduction proper is yeast budding, in which a small protrusion appears on the surface of the mother cell after nuclear division, into which one of the nuclei moves, after which a new small cell is laced off. Thus, the ability of the mother cell to further division is preserved, and the number of individuals increases rapidly.
Vegetative reproduction can be carried out in the form of budding, fragmentation, poly-embryony, etc. When budding, the hydra forms a protrusion of the body wall, which gradually increases in size, at the front end a mouth opening breaks through, surrounded by tentacles. It ends with the formation of a small hydra, which then separates from the mother's organism. Budding is also characteristic of a number of coral polyps and annelids.
Fragmentation is accompanied by the division of the body into two or more parts, and full-fledged individuals (jellyfish, sea anemones, flat and annelids, echinoderms) develop from each.
In polyembryony, the embryo, formed as a result of fertilization, is divided into several embryos. This phenomenon occurs regularly in armadillos, but can also occur in humans in the case of identical twins.
The ability for vegetative propagation is most highly developed in plants in which tubers, bulbs, rhizomes, root suckers, mustaches, and even brood buds can give rise to a new organism.
Asexual reproduction requires only one parent, which saves the time and energy required to find a sexual partner. In addition, new individuals can arise from each fragment of the mother's organism, which also saves the matter and energy spent on reproduction. The rate of asexual reproduction is also quite high, for example, bacteria are able to divide every 20-30 minutes, increasing their numbers extremely quickly. With this method of reproduction, genetically identical descendants are formed - clones, which can be considered as an advantage, provided that environmental conditions remain constant.
However, due to the fact that random mutations are the only source of genetic variability, the almost complete absence of variability among descendants reduces their adaptability to new environmental conditions during settlement and, as a result, they die in much larger numbers than during sexual reproduction.
sexual reproduction- a method of reproduction in which the formation and fusion of germ cells, or gametes, into one cell - a zygote, from which a new organism develops.
If during sexual reproduction somatic cells with a diploid set of chromosomes (in humans 2n = 46) would merge, then already in the second generation the cells of the new organism would already contain a tetraploid set (in humans 4n = 92), in the third - octaploid, etc. .
However, the dimensions of a eukaryotic cell are not unlimited, they should fluctuate within 10-100 microns, since with smaller cell sizes it will not contain a complete set of substances and structures necessary for its vital activity, and with large sizes, the uniform supply of the cell with oxygen, carbon dioxide, water and other necessary substances. Accordingly, the size of the nucleus, in which the chromosomes are located, cannot exceed 1/5-1/10 of the volume of the cell, and if these conditions are violated, the cell will no longer be able to exist. Thus, for sexual reproduction, a preliminary decrease in the number of chromosomes is necessary, which will be restored during fertilization, which is ensured by the process of meiotic cell division.
The decrease in the number of chromosomes must also be strictly ordered and equivalent, since if a new organism does not have complete pairs of chromosomes with their total normal number, then it will either not be viable, or this will be accompanied by the development of serious diseases.
Thus, meiosis provides a decrease in the number of chromosomes, which is restored during fertilization, maintaining the constancy of the karyotype as a whole.
Special forms of sexual reproduction are parthenogenesis and conjugation. In parthenogenesis, or virgin development, a new organism develops from an unfertilized egg, as, for example, in daphnia, honey bees, and some rock lizards. Sometimes this process is stimulated by the introduction of sperm from organisms of another species.
In the process of conjugation, which is typical, for example, for ciliates, individuals exchange fragments of hereditary information, and then reproduce asexually. Strictly speaking, conjugation is a sexual process, not an example of sexual reproduction.
The existence of sexual reproduction requires the production of at least two types of germ cells: male and female. Animal organisms in which male and female sex cells are produced by different individuals are called dioecious, while those capable of producing both types of gametes - hermaphrodites. Hermaphroditism is characteristic of many flat and annelids, gastropods.
Plants in which male and female flowers or other reproductive organs of different names are located on different individuals are called dioecious, and having both types of flowers at the same time - monoecious.
Sexual reproduction ensures the emergence of genetic diversity of offspring, which is based on meiosis and recombination of parental genes during fertilization. The most successful combinations of genes provide the best adaptation of descendants to the environment, their survival and a greater probability of passing on their hereditary information to the next generations. This process leads to a change in the characteristics and properties of organisms and, ultimately, to the formation of new species in the process of evolutionary natural selection.
At the same time, matter and energy are used inefficiently during sexual reproduction, since organisms are often forced to produce millions of gametes, but only a few of them are used during fertilization. In addition, it is necessary to expend energy on providing other conditions. For example, plants form flowers and produce nectar to attract animals that carry pollen to the female parts of other flowers, and animals spend a lot of time and energy searching for mates and courtship. Then a lot of energy has to be expended in caring for offspring, since in sexual reproduction the offspring are often so small at first that many of them die from predators, starvation, or simply because of unfavorable conditions. Therefore, during asexual reproduction, energy costs are much less. Nevertheless, sexual reproduction has at least one invaluable advantage - the genetic variability of the offspring.
Asexual and sexual reproduction are widely used by humans in agriculture, ornamental animal husbandry, plant growing and other areas to breed new varieties of plants and animal breeds, preserve economically valuable traits, and also rapidly increase the number of individuals.
In asexual reproduction of plants, along with traditional methods - cuttings, grafting and propagation by layering, modern methods associated with the use of tissue culture are gradually occupying a leading position. In this case, new plants are obtained from small fragments of the mother plant (cells or pieces of tissue) grown on a nutrient medium containing all the nutrients and hormones necessary for the plant. These methods make it possible not only to quickly propagate plant varieties with valuable traits, such as potatoes resistant to leafroll, but also to obtain organisms that are not infected with viruses and other plant pathogens. Tissue culture also underlies the production of so-called transgenic or genetically modified organisms, as well as the hybridization of somatic plant cells that cannot be crossed in any other way.
Crossing plants of different varieties makes it possible to obtain organisms with new combinations of economically valuable traits. For this, pollination by pollen of plants of the same or another species and even genus is used. This phenomenon is called distant hybridization.
Since higher animals lack the ability to naturally reproduce asexually, their main mode of reproduction is sexual. For this, crossing of individuals of both the same species (breed) and interspecific hybridization are used, which results in such well-known hybrids as a mule and a hinny, depending on which individuals of which species were taken as mothers - a donkey and a horse. However, interspecific hybrids are often sterile, that is, unable to produce offspring, so each time they should be bred anew.
For the reproduction of farm animals, artificial parthenogenesis is also used. The outstanding Russian geneticist B. L. Astaurov, by raising the temperature, caused a greater yield of female silkworms, which weave cocoons from a finer and more valuable thread than males.
Cloning can also be considered asexual reproduction, since it uses the nucleus of a somatic cell, which is introduced into a fertilized egg with a killed nucleus. The developing organism must be a copy or clone of an already existing organism.
Fertilization in flowering plants and vertebrates
Fertilization- this is the process of fusion of male and female germ cells to form a zygote.
In the process of fertilization, first the recognition and physical contact of male and female gametes occurs, then the fusion of their cytoplasm, and only at the last stage the hereditary material is combined. Fertilization allows you to restore the diploid set of chromosomes, reduced in the process of formation of germ cells.
Most often in nature, fertilization by male reproductive cells of another organism occurs, however, in a number of cases, penetration of one's own spermatozoa is also possible - self-fertilization. From an evolutionary point of view, self-fertilization is less beneficial, since the probability of the emergence of new combinations of genes is minimal. Therefore, even in most hermaphroditic organisms, cross-fertilization occurs. This process is inherent in both plants and animals, however, there are a number of differences in its course in the aforementioned organisms.
So, in flowering plants, fertilization is preceded by pollination- transfer of pollen containing male sex cells - sperm - on the stigma of the pistil. There it germinates, forming a pollen tube with two sperm moving along it. Having reached the embryo sac, one sperm fuses with the egg to form a zygote, and the other with the central cell (2n), giving rise to the subsequent storage tissue of the secondary endosperm. This method of fertilization is called double fertilization(Fig. 3.4).
In animals, in particular vertebrates, fertilization is preceded by the convergence of gametes, or insemination. The success of insemination is facilitated by the synchronization of the excretion of male and female germ cells, as well as the release of specific chemicals by the eggs in order to facilitate the orientation of spermatozoa in space.
When cultivating cultivated plants and domestic animals, human efforts are mainly aimed at preserving and multiplying economically valuable traits, while the resistance of these organisms to environmental conditions and overall viability are reduced. In addition, soybeans and many other crops are self-pollinating, so human intervention is needed to develop new varieties. There may also be difficulties in the process of fertilization itself, since some plants and animals may have genes for sterility.
Plants for breeding purposes produce artificial pollination, for which the stamens are removed from the flowers, and then pollen from other flowers is applied to the stigmas of the pistils and pollinated flowers are covered with insulator caps to prevent pollination by pollen from other plants. In some cases, artificial pollination is carried out to increase yields, since seeds and fruits do not develop from the ovaries of unpollinated flowers. This technique was previously practiced in sunflower crops.
With distant hybridization, especially if the plants differ in the number of chromosomes, natural fertilization becomes either completely impossible, or already at the first cell division, chromosome segregation is disturbed and the organism dies. In this case, fertilization is carried out under artificial conditions, and at the beginning of division, the cell is treated with colchicine, a substance that destroys the division spindle, while the chromosomes are scattered around the cell, and then a new nucleus is formed with a doubled number of chromosomes, and during subsequent divisions such problems do not arise. Thus, the rare cabbage hybrid G.D. Karpechenko and triticale, a high-yielding hybrid of wheat and rye, were created.
In the main types of farm animals, there are even more obstacles to fertilization than in plants, which forces man to take drastic measures. Artificial insemination is used mainly in the breeding of valuable breeds, when it is necessary to obtain as many offspring as possible from one producer. In these cases, the seminal fluid is collected, mixed with water, placed in ampoules, and then, as necessary, injected into the genital tract of females. In fish farms, during artificial insemination in fish, male sperm obtained from milk is mixed with caviar in special containers. Juveniles grown in special cages are then released into natural water bodies and restore the population, for example, of sturgeons in the Caspian Sea and on the Don.
Thus, artificial insemination serves a person to obtain new, highly productive varieties of plants and animal breeds, as well as to increase their productivity and restore natural populations.
External and internal fertilization
Animals distinguish between external and internal fertilization. At external fertilization female and male germ cells are brought out, where the process of their fusion takes place, as, for example, in annelids, bivalves, non-cranial, most fish and many amphibians. Despite the fact that it does not require the approach of breeding individuals, in mobile animals not only their approach is possible, but also accumulation, as in the spawning of fish.
Internal fertilization is associated with the introduction of male reproductive products into the female genital tract, and an already fertilized egg is excreted outside. It often has dense shells that prevent damage and penetration of the following spermatozoa. Internal fertilization is characteristic of the vast majority of terrestrial animals, for example, flat and round worms, many arthropods and gastropods, reptiles, birds and mammals, as well as a number of amphibians. It is also found in some aquatic animals, including cephalopods and cartilaginous fish.
There is also an intermediate type of fertilization - external-internal, in which the female captures the reproductive products specially left by the male on some substrate, as occurs in some arthropods and tailed amphibians. External-internal fertilization can be considered as transitional from external to internal.
Both external and internal fertilization have their advantages and disadvantages. So, during external fertilization, germ cells are released into water or air, as a result of which the vast majority of them die. However, this type of fertilization ensures the existence of sexual reproduction in such attached and inactive animals as bivalves and non-cranial molluscs. With internal fertilization, the loss of gametes is, of course, much less, however, at the same time, matter and energy are spent on finding a partner, and the offspring that are born are often too small and weak and require long-term parental care.
3.3. Ontogeny and its inherent regularities. Specialization of cells, formation of tissues, organs. Embryonic and postembryonic development of organisms. Life cycles and alternation of generations. Causes of disruption in the development of organisms.
Ontogeny and its inherent patterns
Ontogenesis(from Greek. ontos- existent and genesis- emergence, origin) is the process of individual development of an organism from birth to death. This term was introduced in 1866 by the German scientist E. Haeckel (1834-1919).
The origin of an organism is considered to be the appearance of a zygote as a result of the fertilization of an egg by a spermatozoon, although a zygote as such is not formed during parthenogenesis. In the process of ontogenesis, growth, differentiation and integration of parts of the developing organism occur. Differentiation(from lat. trim- difference) is the process of the emergence of differences between homogeneous tissues and organs, their changes in the course of the development of an individual, leading to the formation of specialized tissues and organs.
Patterns of ontogeny are the subject of study embryology(from Greek. embryo- germ and logos- word, science). A significant contribution to its development was made by Russian scientists K. Baer (1792-1876), who discovered the egg cell of mammals and put embryological evidence as the basis for the classification of vertebrates, A. O. Kovalevsky (1849-1901) and I. I. Mechnikov (1845-1916 ) - the founders of the theory of germ layers and comparative embryology, as well as A. N. Severtsov (1866-1936), who put forward the theory of the emergence of new characters at any stage of ontogenesis.
Individual development is typical only for multicellular organisms, since in unicellular organisms growth and development end at the level of a single cell, and differentiation is completely absent. The course of ontogenesis is determined by genetic programs fixed in the process of evolution, that is, ontogenesis is a brief repetition of the historical development of a given species, or phylogenesis.
Despite the inevitable switching of individual groups of genes in the course of individual development, all changes in the body occur gradually and do not violate its integrity, however, the events of each previous stage have a significant impact on the course of subsequent stages of development. Thus, any failures in the process of development can lead to interruption of the process of ontogenesis at any of the stages, as is often the case with embryos (the so-called miscarriages).
Thus, the process of ontogenesis is characterized by the unity of space and time of action, since it is inextricably linked with the body of the individual and proceeds unidirectionally.
Embryonic and postembryonic development of organisms
Periods of ontogeny
There are several periods of ontogeny, but most often in the ontogeny of animals, the embryonic and postembryonic periods are distinguished.
Embryonic period begins with the formation of a zygote in the process of fertilization and ends with the birth of an organism or its release from the embryonic (egg) membranes.
Postembryonic period lasts from birth to death. Sometimes isolated and proembryonic period, or progenesis, which include gametogenesis and fertilization.
embryonic development, or embryogenesis, in animals and humans are divided into a number of stages: cleavage, gastrulation, histogenesis and organogenesis, as well as period of differentiated embryo.
Splitting up- this is the process of mitotic division of the zygote into ever smaller cells - blastomeres (Fig. 3.5). First, two cells are formed, then four, eight, etc. The decrease in cell size is mainly due to the fact that in the interphase of the cell cycle, for various reasons, there is no Gj-period, in which an increase in the size of daughter cells should occur. This process is similar to breaking ice, but it is not chaotic, but strictly ordered. For example, in humans, this fragmentation is bilateral, that is, bilaterally symmetrical. As a result of crushing and subsequent divergence of cells, a blastula- a single-layer multicellular embryo, which is a hollow ball, the walls of which are formed by cells - blastomeres, and the cavity inside is filled with liquid and is called blastocoele.
Gastrulation called the process of formation of a two- or three-layer embryo - gastrulae(from Greek. gaster- stomach), which occurs immediately after the formation of the blastula. Gastrulation is carried out by the movement of cells and their groups relative to each other, for example, by invagination of one of the walls of the blastula. In addition to two or three layers of cells, the gastrula also has a primary mouth - blastopore.
The layers of cells in the gastrula are called germ layers. There are three germ layers: ectoderm, mesoderm and endoderm. ectoderm(from Greek. ectos outside, outside and dermis- skin) is the outer germ layer, mesoderm(from Greek. mezos- medium, intermediate) - medium, and endoderm(from Greek. enthos- inside) - internal.
Despite the fact that all cells of a developing organism originate from a single cell - a zygote - and contain the same set of genes, that is, they are its clones, since they are formed as a result of mitotic division, the gastrulation process is accompanied by cell differentiation. Differentiation is due to the switching of groups of genes in different parts of the embryo and the synthesis of new proteins, which later determine the specific functions of the cell and leave an imprint on its structure.
The specialization of cells is imprinted by the proximity of other cells, as well as the hormonal background. For example, if a fragment on which a notochord develops from one frog embryo is transplanted to another, this will cause the formation of a rudiment of the nervous system in the wrong place, and a double embryo will begin to form, as it were. This phenomenon has been named embryonic induction.
Histogenesis call the process of formation of mature tissues inherent in an adult organism, and organogenesis- the process of formation of organs.
In the process of histo- and organogenesis, skin epithelium and its derivatives (hair, nails, claws, feathers), oral cavity epithelium and tooth enamel, rectum, nervous system, sensory organs, gills, etc. are formed from the ectoderm. Endoderm derivatives are the intestines and related with it the glands (liver and pancreas), as well as the lungs. And the mesoderm gives rise to all types of connective tissue, including bone and cartilage tissues of the skeleton, muscle tissue of skeletal muscles, the circulatory system, many endocrine glands, etc.
The laying of the neural tube on the dorsal side of the embryo of chordates symbolizes the beginning of another intermediate stage of development - neurula(novolat. neurula, reduce, from the Greek. neuron- nerve). This process is also accompanied by the laying of a complex of axial organs, such as a chord.
After the course of organogenesis, a period begins differentiated embryo, which is characterized by continued specialization of body cells and rapid growth.
In many animals, in the process of embryonic development, embryonic membranes and other temporary organs arise that are not useful in subsequent development, such as the placenta, umbilical cord, etc.
The postembryonic development of animals according to the ability to reproduce is divided into pre-reproductive (juvenile), reproductive and post-reproductive periods.
Juvenile period lasts from birth to puberty, it is characterized by intensive growth and development of the body.
The growth of the organism occurs due to an increase in the number of cells due to division and an increase in their size. There are two main types of growth: limited and unlimited. Limited, or indoor growth occurs only at certain periods of life, mainly before puberty. It is typical for most animals. For example, a person grows mainly until the age of 13-15, although the final formation of the body occurs before the age of 25. unlimited, or open growth continues throughout the life of the individual, as in plants and some fish. There are also periodic and non-periodic growth.
Growth processes are controlled by the endocrine, or hormonal system: in humans, an increase in the linear dimensions of the body is facilitated by the release of somatotropic hormone, while gonadotropic hormones largely suppress it. Similar mechanisms have been discovered in insects, which have a special juvenile hormone and a molting hormone.
In flowering plants, embryonic development occurs after double fertilization, in which one sperm fertilizes the egg, and the second fertilizes the central cell. From the zygote, an embryo is formed, which undergoes a series of divisions. After the first division, the embryo itself is formed from one cell, and the pendants are formed from the second, through which the embryo is supplied with nutrients. The central cell gives rise to a triploid endosperm containing nutrients for the development of the embryo (Fig. 3.7).
Embryonic and postembryonic development of seed plants are often separated in time because they require certain conditions for germination. The postembryonic period in plants is divided into vegetative, generative and aging periods. In the vegetative period, an increase in the biomass of the plant occurs, in the generative period they acquire the ability to sexual reproduction (in seed plants, to flowering and fruiting), while during the aging period, the ability to reproduce is lost.
Life cycles and alternation of generations
Newly formed organisms do not immediately acquire the ability to reproduce their own kind.
Life cycle- a set of stages of development, starting from the zygote, after which the body reaches maturity and acquires the ability to reproduce.
In the life cycle, there is an alternation of developmental stages with haploid and diploid sets of chromosomes, while in higher plants and animals the diploid set predominates, while in lower plants it is vice versa.
Life cycles can be simple or complex. Unlike a simple life cycle, in a complex one, sexual reproduction alternates with parthenogenetic and asexual reproduction. For example, daphnia crustaceans, which give asexual generations during the summer, reproduce sexually in autumn. The life cycles of some fungi are especially complex. In a number of animals, the alternation of sexual and asexual generations occurs regularly, and such a life cycle is called correct. It is typical, for example, for a number of jellyfish.
The duration of the life cycle is determined by the number of generations developing during the year, or the number of years during which the organism carries out its development. For example, plants are divided into annuals and perennials.
Knowledge of life cycles is necessary for genetic analysis, since in the haploid and diploid states the action of genes is revealed in different ways: in the first case, there are great opportunities for the expression of all genes, while in the second, some genes are not detected.
Causes of impaired development of organisms
The ability to self-regulate and to resist the harmful influences of the environment does not appear in organisms immediately. During embryonic and postembryonic development, when many of the body's defense systems have not yet formed, organisms are usually vulnerable to damaging factors. Therefore, in animals and plants, the embryo is protected by special shells or by the maternal organism itself. It is either supplied with a special nourishing tissue, or receives nutrients directly from the mother's organism. Nevertheless, a change in external conditions can accelerate or slow down the development of the embryo and even cause various disorders.
Factors that cause deviations in the development of the embryo are called teratogenic, or teratogens. Depending on the nature of these factors, they are divided into physical, chemical and biological.
TO physical factors First of all, ionizing radiation, which provokes numerous mutations in the fetus, which may be incompatible with life, is one of them.
Chemical teratogens are heavy metals, benzapyrene emitted by cars and industrial plants, phenols, a number of drugs, alcohol, drugs and nicotine.
The use of alcohol, drugs, and tobacco smoking by parents has a particularly harmful effect on the development of a human embryo, since alcohol and nicotine inhibit cellular respiration. Insufficient supply of oxygen to the embryo leads to the fact that a smaller number of cells are formed in the developing organs, the organs are underdeveloped. The nervous tissue is especially sensitive to the lack of oxygen. The future mother's use of alcohol, drugs, tobacco smoking, drug abuse often leads to irreversible damage to the embryo and the subsequent birth of children with mental retardation or congenital deformities.
3.4. Genetics, its tasks. Heredity and variability are properties of organisms. Basic genetic concepts.
Genetics, its tasks
The successes of natural science and cell biology in the 18th-19th centuries allowed a number of scientists to speculate about the existence of certain hereditary factors that determine, for example, the development of hereditary diseases, but these assumptions were not supported by appropriate evidence. Even the theory of intracellular pangenesis formulated by X. de Vries in 1889, which assumed the existence of certain “pangenes” in the cell nucleus that determine the hereditary inclinations of the organism, and the release into the protoplasm of only those of them that determine the cell type, could not change the situation, as well as the theory of "germ plasm" by A. Weisman, according to which the traits acquired in the process of ontogenesis are not inherited.
Only the works of the Czech researcher G. Mendel (1822-1884) became the foundation stone of modern genetics. However, despite the fact that his works were cited in scientific publications, contemporaries did not pay attention to them. And only the rediscovery of the patterns of independent inheritance by three scientists at once - E. Chermak, K. Correns and H. de Vries - forced the scientific community to turn to the origins of genetics.
Genetics is a science that studies the laws of heredity and variability and methods of managing them.
The tasks of genetics at the present stage are the study of the qualitative and quantitative characteristics of the hereditary material, the analysis of the structure and functioning of the genotype, the decoding of the fine structure of the gene and methods for regulating gene activity, the search for genes that cause the development of human hereditary diseases and methods for their "correction", the creation of a new generation of drugs by type DNA vaccines, the construction of organisms with new properties using genetic and cell engineering tools that could produce drugs and food necessary for humans, as well as a complete decoding of the human genome.
Heredity and variability - properties of organisms
Heredity- is the ability of organisms to transmit their characteristics and properties in a number of generations.
Variability- the property of organisms to acquire new characteristics during life.
signs- these are any morphological, physiological, biochemical and other features of organisms in which some of them differ from others, for example, eye color. properties They also call any functional features of organisms, which are based on a certain structural feature or a group of elementary features.
Organisms can be divided into quality And quantitative. Qualitative signs have two or three contrasting manifestations, which are called alternative features, for example, blue and brown eyes, while quantitative ones (milk yield of cows, wheat yield) do not have clearly defined differences.
The material carrier of heredity is DNA. There are two types of heredity in eukaryotes: genotypic And cytoplasmic. Carriers of genotypic heredity are localized in the nucleus, and further we will talk about it, and carriers of cytoplasmic heredity are circular DNA molecules located in mitochondria and plastids. Cytoplasmic inheritance is transmitted mainly with the egg, therefore it is also called maternal.
A small number of genes are localized in the mitochondria of human cells, but their change can have a significant impact on the development of the organism, for example, lead to the development of blindness or a gradual decrease in mobility. Plastids play an equally important role in plant life. So, in some parts of the leaf, chlorophyll-free cells may be present, which leads, on the one hand, to a decrease in plant productivity, and on the other hand, such variegated organisms are valued in decorative gardening. Such specimens are reproduced mainly asexually, since ordinary green plants are more often obtained during sexual reproduction.
Genetic methods
The hybridological method, or the method of crosses, consists in the selection of parental individuals and the analysis of offspring. At the same time, the genotype of an organism is judged by the phenotypic manifestations of genes in offspring obtained by a certain crossing scheme. This is the oldest informative method of genetics, which was most fully applied for the first time by G. Mendel in combination with the statistical method. This method is not applicable in human genetics for ethical reasons.
The cytogenetic method is based on the study of the karyotype: the number, shape and size of the body's chromosomes. The study of these features makes it possible to identify various developmental pathologies.
The biochemical method allows you to determine the content of various substances in the body, especially their excess or deficiency, as well as the activity of a number of enzymes.
Molecular genetic methods are aimed at identifying variations in the structure and deciphering the primary nucleotide sequence of the studied DNA sections. They allow you to identify genes for hereditary diseases even in embryos, establish paternity, etc.
The population-statistical method makes it possible to determine the genetic composition of a population, the frequency of certain genes and genotypes, the genetic burden, and also to outline the prospects for the development of a population.
The method of hybridization of somatic cells in culture allows you to determine the localization of certain genes in chromosomes when cells of various organisms merge, for example, mice and hamsters, mice and humans, etc.
Basic genetic concepts and symbolism
Gene- This is a section of a DNA molecule, or chromosome, that carries information about a certain trait or property of an organism.
Some genes can influence the manifestation of several traits at once. Such a phenomenon is called pleiotropy. For example, the gene that determines the development of the hereditary disease arachnodactyly (spider fingers) causes the curvature of the lens, the pathology of many internal organs.
Each gene occupies a strictly defined place in the chromosome - locus. Since in the somatic cells of most eukaryotic organisms the chromosomes are paired (homologous), each of the paired chromosomes contains one copy of the gene responsible for a particular trait. Such genes are called allelic.
Allelic genes most often exist in two versions - dominant and recessive. Dominant called an allele that manifests itself regardless of which gene is on the other chromosome, and suppresses the development of a trait encoded by a recessive gene. Dominant alleles are usually denoted by capital letters of the Latin alphabet (A, B, C and etc.), and recessive - lowercase (a, b, from and etc.)- recessive alleles can only be expressed if they occupy loci on both paired chromosomes.
An organism that has the same allele on both homologous chromosomes is called homozygous for that gene, or homozygous ( AA , aa, AABB,aabb etc.), and an organism in which both homologous chromosomes contain different variants of the gene - dominant and recessive - is called heterozygous for that gene, or heterozygous (Aa, AaBb etc.).
A number of genes can have three or more structural variants, for example, blood groups according to the ABO system are encoded by three alleles - I A , I B , i. Such a phenomenon is called multiple allelism. However, even in this case, each chromosome from a pair carries only one allele, that is, all three gene variants in one organism cannot be represented.
Genome- a set of genes characteristic of a haploid set of chromosomes.
Genotype- a set of genes characteristic of a diploid set of chromosomes.
Phenotype- a set of signs and properties of an organism, which is the result of the interaction of the genotype and the environment.
Since organisms differ from each other in many traits, it is possible to establish the patterns of their inheritance only by analyzing two or more traits in the offspring. Crossing, in which inheritance is considered and an accurate quantitative account of offspring is carried out for one pair of alternative traits, is called monohybrid, for two pairs dihybrid, for more signs polyhybrid.
According to the phenotype of an individual, it is far from always possible to establish its genotype, since both an organism homozygous for the dominant gene (AA) and heterozygous (Aa) will have a manifestation of the dominant allele in the phenotype. Therefore, to check the genotype of an organism with cross-fertilization, analyzing cross- crossing, in which an organism with a dominant trait is crossed with a homozygous recessive gene. In this case, an organism homozygous for the dominant gene will not produce splitting in the offspring, while in the offspring of heterozygous individuals an equal number of individuals with dominant and recessive traits is observed.
The following conventions are most often used to write crossover schemes:
R (from lat. parent- parents) - parent organisms;
♀ (alchemical sign of Venus - a mirror with a handle) - maternal individual;
♂ (alchemical sign of Mars - shield and spear) - paternal individual;
x - crossing sign;
F 1, F 2, F 3, etc. - hybrids of the first, second, third and subsequent generations;
F a - offspring from analyzing crosses.
Chromosomal theory of heredity
The founder of genetics G. Mendel, as well as his closest followers, had no idea about the material basis of hereditary inclinations, or genes. However, already in 1902-1903, the German biologist T. Boveri and the American student W. Setton independently suggested that the behavior of chromosomes during cell maturation and fertilization makes it possible to explain the splitting of hereditary factors according to Mendel, i.e., in their opinion, genes must be located on the chromosomes. These assumptions have become the cornerstone of the chromosome theory of heredity.
In 1906, the English geneticists W. Batson and R. Pennet discovered a violation of Mendelian splitting when crossing sweet peas, and their compatriot L. Doncaster, in experiments with the gooseberry moth butterfly, discovered sex-linked inheritance. The results of these experiments clearly contradicted Mendelian ones, but given that by that time it was already known that the number of known features for experimental objects far exceeded the number of chromosomes, and this suggested that each chromosome carries more than one gene, and the genes of one chromosome are inherited together.
In 1910, the experiments of T. Morgan's group began on a new experimental object - the Drosophila fruit fly. The results of these experiments made it possible by the mid-20s of the 20th century to formulate the main provisions of the chromosome theory of heredity, to determine the order of arrangement of genes in chromosomes and the distance between them, i.e., to compile the first maps of chromosomes.
The main provisions of the chromosome theory of heredity:
1) Genes are located on chromosomes. Genes on the same chromosome are inherited together, or linked, and are called clutch group. The number of linkage groups is numerically equal to the haploid set of chromosomes.
Each gene occupies a strictly defined place in the chromosome - a locus.
Genes are arranged linearly on chromosomes.
Disruption of gene linkage occurs only as a result of crossing over.
The distance between genes on a chromosome is proportional to the percentage of crossing over between them.
Independent inheritance is characteristic only for genes of non-homologous chromosomes.
Modern ideas about the gene and genome
In the early 40s of the 20th century, J. Beadle and E. Tatum, analyzing the results of genetic studies conducted on the neurospore fungus, came to the conclusion that each gene controls the synthesis of an enzyme, and formulated the principle "one gene - one enzyme" .
However, already in 1961 F. Jacob, J.-L. Mono and A. Lvov managed to decipher the structure of the Escherichia coli gene and study the regulation of its activity. For this discovery, they were awarded the Nobel Prize in Physiology or Medicine in 1965.
In the course of the study, in addition to structural genes that control the development of certain traits, they were able to identify regulatory ones, the main function of which is the manifestation of traits encoded by other genes.
The structure of the prokaryotic gene. The structural gene of prokaryotes has a complex structure, since it includes regulatory regions and coding sequences. Regulatory regions include the promoter, operator, and terminator (Figure 3.8). promoter called the region of the gene to which the RNA polymerase enzyme is attached, which ensures the synthesis of mRNA during transcription. FROM operator, located between the promoter and the structural sequence, can bind repressor protein, which does not allow RNA polymerase to start reading hereditary information from the coding sequence, and only its removal allows transcription to begin. The structure of the repressor is usually encoded in a regulatory gene located in another part of the chromosome. The reading of information ends at a section of the gene called terminator.
coding sequence structural gene contains information about the sequence of amino acids in the corresponding protein. The coding sequence in prokaryotes is called cistronome, and the totality of coding and regulatory regions of the prokaryotic gene - operon. In general, prokaryotes, which include E. coli, have a relatively small number of genes located on a single ring chromosome.
The cytoplasm of prokaryotes may also contain additional small circular or open DNA molecules called plasmids. Plasmids are able to integrate into chromosomes and be transferred from one cell to another. They can carry information about sexual characteristics, pathogenicity, and antibiotic resistance.
The structure of the eukaryotic gene. Unlike prokaryotes, eukaryotic genes do not have an operon structure, since they do not contain an operator, and each structural gene is accompanied only by a promoter and a terminator. In addition, significant regions in eukaryotic genes ( exons) alternate with insignificant ( introns), which are completely transcribed into mRNAs and then excised during their maturation. The biological role of introns is to reduce the likelihood of mutations in significant areas. Eukaryotic gene regulation is much more complex than that described for prokaryotes.
The human genome. In each human cell, there are about 2 m of DNA in 46 chromosomes, tightly packed in a double helix, which consists of approximately 3.2 x 10 9 nucleotide pairs, which provides about 10 1900000000 possible unique combinations. By the end of the 1980s, the location of about 1,500 human genes was known, but their total number was estimated at about 100,000, since only about 10,000 hereditary diseases in humans, not to mention the number of various proteins contained in cells .
In 1988, the international project "Human Genome" was launched, which by the beginning of the 21st century ended with a complete decoding of the nucleotide sequence. He made it possible to understand that two different people have 99.9% similar nucleotide sequences, and only the remaining 0.1% determine our individuality. In total, approximately 30-40 thousand structural genes were discovered, but then their number was reduced to 25-30 thousand. Among these genes there are not only unique, but also repeated hundreds and thousands of times. However, these genes encode a much larger number of proteins, such as tens of thousands of protective proteins - immunoglobulins.
97% of our genome is genetic "garbage" that exists only because it can reproduce well (the RNA that is transcribed in these regions never leaves the nucleus). For example, among our genes there are not only "human" genes, but also 60% of genes similar to those of the fruit fly, and up to 99% of our genes are related to chimpanzees.
In parallel with the decoding of the genome, chromosome mapping also took place, as a result of which it was possible not only to detect, but also to determine the location of some genes responsible for the development of hereditary diseases, as well as drug target genes.
The deciphering of the human genome does not yet have a direct effect, since we have received a kind of instruction for assembling such a complex organism as a person, but have not learned how to make it or at least correct errors in it. Nevertheless, the era of molecular medicine is already on the threshold, all over the world there is a development of so-called gene preparations that can block, remove or even replace pathological genes in living people, and not just in a fertilized egg.
We should not forget that in eukaryotic cells DNA is contained not only in the nucleus, but also in mitochondria and plastids. Unlike the nuclear genome, the organization of mitochondrial and plastid genes has much in common with the organization of the prokaryotic genome. Despite the fact that these organelles carry less than 1% of the cell's hereditary information and do not even encode a complete set of proteins necessary for their own functioning, they can significantly affect some features of the body. Thus, variegation in plants of chlorophytum, ivy and others is inherited by an insignificant number of descendants, even when two variegated plants are crossed. This is due to the fact that plastids and mitochondria are transmitted mostly with the cytoplasm of the egg, so this heredity is called maternal, or cytoplasmic, in contrast to the genotypic, which is localized in the nucleus.
3.5. Patterns of heredity, their cytological basis. Mono- and dihybrid crossing. Patterns of inheritance established by G. Mendel. Linked inheritance of traits, violation of the linkage of genes. Laws of T. Morgan. Chromosomal theory of heredity. Sex genetics. Inheritance of sex-linked traits. The genotype as an integral system. Development of knowledge about the genotype. The human genome. Interaction of genes. Solution of genetic problems. Drawing up cross-breeding schemes. G. Mendel's laws and their cytological foundations.
Patterns of heredity, their cytological basis
According to the chromosomal theory of heredity, each pair of genes is localized in a pair of homologous chromosomes, and each of the chromosomes carries only one of these factors. If we imagine that genes are point objects on straight chromosomes, then schematically homozygous individuals can be written as A||A or a||a, while heterozygous - A||a. During the formation of gametes during meiosis, each of the genes of a heterozygote pair will be in one of the germ cells (Fig. 3.9).
For example, if two heterozygous individuals are crossed, then, provided that each of them has only a pair of gametes, it is possible to obtain only four daughter organisms, three of which will carry at least one dominant gene BUT, and only one will be homozygous for the recessive gene but, i.e., the patterns of heredity are statistical in nature (Fig. 3.10).
In cases where the genes are located on different chromosomes, then during the formation of gametes, the distribution between them of alleles from a given pair of homologous chromosomes occurs completely independently of the distribution of alleles from other pairs (Fig. 3.11). It is the random arrangement of homologous chromosomes at the spindle equator in metaphase I of meiosis and their subsequent divergence in anaphase I that leads to the diversity of allele recombination in gametes.
The number of possible combinations of alleles in male or female gametes can be determined by the general formula 2 n, where n is the number of chromosomes characteristic of the haploid set. In humans, n \u003d 23, and the possible number of combinations is 2 23 \u003d 8388608. The subsequent union of gametes during fertilization is also random, and therefore independent splitting for each pair of characters can be recorded in the offspring (Fig. 3.11).
However, the number of traits in each organism is many times greater than the number of its chromosomes, which can be distinguished under a microscope, therefore, each chromosome must contain many factors. If we imagine that a certain individual, heterozygous for two pairs of genes located in homologous chromosomes, produces gametes, then one should take into account not only the probability of formation of gametes with the original chromosomes, but also gametes that have received chromosomes changed as a result of crossing over in prophase I of meiosis. Consequently, new combinations of traits will arise in the offspring. The data obtained in experiments on Drosophila formed the basis chromosome theory of heredity.
Another fundamental confirmation of the cytological basis of heredity was obtained in the study of various diseases. So, in humans, one of the forms of cancer is due to the loss of a small section of one of the chromosomes.
Patterns of inheritance established by G. Mendel, their cytological foundations (mono- and dihybrid crossing)
The main patterns of independent inheritance of traits were discovered by G. Mendel, who achieved success by applying in his research a new at that time hybridological method.
The success of G. Mendel was ensured by the following factors:
1. a good choice of the object of study (sowing pea), which has a short growing season, is a self-pollinating plant, produces a significant amount of seeds and is represented by a large number of varieties with well distinguishable characteristics;
2. using only pure pea lines, which for several generations did not give splitting of traits in the offspring;
3. concentration on only one or two signs;
4. planning the experiment and drawing up clear crossing schemes;
5. accurate quantitative calculation of the resulting offspring.
For the study, G. Mendel selected only seven signs that have alternative (contrasting) manifestations. Already in the first crossings, he noticed that in the offspring of the first generation, when plants with yellow and green seeds were crossed, all the offspring had yellow seeds. Similar results were obtained in the study of other signs (Table 3.1). The signs that prevailed in the first generation, G. Mendel called dominant. Those of them that did not appear in the first generation were called recessive.
Individuals that gave splitting in the offspring were called heterozygous, and individuals that did not give splitting - homozygous.
Table 3.1
Signs of peas, the inheritance of which was studied by G. Mendel
|
sign |
Manifestation option |
|
|
Dominant |
Recessive |
|
|
seed coloring | ||
|
seed shape |
wrinkled |
|
|
Fruit shape (bean) |
jointed |
|
|
fruit coloration | ||
|
Flower corolla color | ||
|
flower position |
axillary |
Apical |
|
stem length |
Short |
|
Crossing, in which the manifestation of only one trait is examined, is called monohybrid. In this case, the patterns of inheritance of only two variants of one trait are traced, the development of which is due to a pair of allelic genes. For example, the trait "corolla color" in peas has only two manifestations - red and white. All other features characteristic of these organisms are not taken into account and are not taken into account in the calculations.
The scheme of monohybrid crossing is as follows:
Crossing two pea plants, one of which had yellow seeds and the other green, in the first generation G. Mendel received plants exclusively with yellow seeds, regardless of which plant was chosen as the mother and which was the father. The same results were obtained in crosses for other traits, which gave G. Mendel reason to formulate the law of uniformity of hybrids of the first generation, which is also called Mendel's first law And the law of dominance.
Mendel's first law:
When crossing homozygous parental forms that differ in one pair of alternative traits, all hybrids of the first generation will be uniform both in genotype and phenotype.
A - yellow seeds; a green seeds.
During self-pollination (crossing) of hybrids of the first generation, it turned out that 6022 seeds are yellow, and 2001 are green, which approximately corresponds to a ratio of 3:1. The discovered regularity is called splitting law, or Mendel's second law.
Mendel's second law:
When crossing heterozygous hybrids of the first generation in the offspring, the predominance of one of the traits will be observed in a ratio of 3:1 by phenotype (1:2:1 by genotype).
However, by the phenotype of an individual, it is far from always possible to establish its genotype, since both homozygotes for the dominant gene (AA) as well as heterozygotes (ah) will have the expression of a dominant gene in the phenotype. Therefore, for organisms with cross-fertilization apply analyzing cross A cross in which an organism with an unknown genotype is crossed with a homozygous recessive gene to test the genotype. At the same time, homozygous individuals for the dominant gene do not give splitting in the offspring, while in the offspring of heterozygous individuals, an equal number of individuals with both dominant and recessive traits is observed:
Based on the results of his own experiments, G. Mendel suggested that hereditary factors do not mix during the formation of hybrids, but remain unchanged. Since the connection between generations is carried out through gametes, he assumed that in the process of their formation only one factor from a pair gets into each of the gametes (i.e., the gametes are genetically pure), and during fertilization, the pair is restored. These assumptions are called gamete purity rules.
Gamete purity rule:
During gametogenesis, the genes of one pair are separated, i.e., each gamete carries only one variant of the gene.
However, organisms differ from each other in many ways, so it is possible to establish patterns of their inheritance only by analyzing two or more traits in the offspring. Crossing, in which inheritance is considered and an accurate quantitative account of the offspring is made according to two pairs of traits, is called dihybrid. If the manifestation of a larger number of hereditary traits is analyzed, then this is already polyhybrid cross.
Dihybrid cross scheme:
With a greater variety of gametes, it becomes difficult to determine the genotypes of descendants, therefore, the Punnett lattice is widely used for analysis, in which male gametes are entered horizontally, and female gametes vertically. The genotypes of the offspring are determined by the combination of genes in columns and rows.
For dihybrid crossing, G. Mendel chose two traits: the color of the seeds (yellow and green) and their shape (smooth and wrinkled). In the first generation, the law of uniformity of hybrids of the first generation was observed, and in the second generation there were 315 yellow smooth seeds, 108 green smooth seeds, 101 yellow wrinkled and 32 green wrinkled. The calculation showed that the splitting approached 9:3:3:1, but the ratio of 3:1 was maintained for each of the signs (yellow - green, smooth - wrinkled). This pattern has been named the law of independent splitting of signs, or Mendel's third law.
Mendel's third law:
When crossing homozygous parental forms that differ in two or more pairs of traits, in the second generation, independent splitting of these traits will occur in a ratio of 3:1 (9:3:3:1 in dihybrid crossing).
Mendel's third law is applicable only to cases of independent inheritance, when genes are located in different pairs of homologous chromosomes. In cases where genes are located in the same pair of homologous chromosomes, patterns of linked inheritance are valid. The patterns of independent inheritance of traits established by G. Mendel are also often violated during the interaction of genes.
Laws of T. Morgan: linked inheritance of traits, violation of gene linkage
The new organism receives from the parents not a scattering of genes, but whole chromosomes, while the number of traits and, accordingly, the genes that determine them is much greater than the number of chromosomes. In accordance with the chromosomal theory of heredity, genes located on the same chromosome are inherited linked. As a result, when dihybrid crossed, they do not give the expected splitting of 9:3:3:1 and do not obey Mendel's third law. One would expect that the linkage of genes is complete, and when crossing individuals homozygous for these genes and in the second generation, it gives the initial phenotypes in a ratio of 3:1, and when analyzing hybrids of the first generation, the splitting should be 1:1.
To test this assumption, the American geneticist T. Morgan chose a pair of genes in Drosophila that control body color (gray - black) and wing shape (long - rudimentary), which are located in one pair of homologous chromosomes. The gray body and long wings are dominant characters. When crossing a homozygous fly with a gray body and long wings and a homozygous fly with a black body and rudimentary wings in the second generation, in fact, mainly parental phenotypes were obtained in a ratio close to 3:1, however, there was also an insignificant number of individuals with new combinations of these traits ( Fig. 3.12).
These individuals are called recombinant. However, after analyzing the crossing of first-generation hybrids with homozygotes for recessive genes, T. Morgan found that 41.5% of individuals had a gray body and long wings, 41.5% had a black body and rudimentary wings, 8.5% had a gray body and rudimentary wings, and 8.5% - black body and rudimentary wings. He associated the resulting splitting with the crossing over occurring in prophase I of meiosis and proposed to consider 1% of the crossing over as a unit of distance between genes in the chromosome, later named after him morganide.
The patterns of linked inheritance, established in the course of experiments on Drosophila, are called T. Morgan's law.
Morgan's Law:
Genes located on the same chromosome occupy a specific place, called a locus, and are inherited in a linked fashion, with the strength of linkage being inversely proportional to the distance between the genes.
Genes located in the chromosome directly one after another (the probability of crossing over is extremely small) are called fully linked, and if there is at least one more gene between them, then they are not completely linked and their linkage is broken during crossing over as a result of the exchange of sections of homologous chromosomes.
The phenomena of gene linkage and crossing over make it possible to build maps of chromosomes with the order of genes plotted on them. Genetic maps of chromosomes have been created for many genetically well-studied objects: Drosophila, mice, humans, corn, wheat, peas, etc. The study of genetic maps allows you to compare the structure of the genome in different types of organisms, which is important for genetics and breeding, as well as evolutionary studies .
Sex Genetics
Floor- this is a combination of morphological and physiological features of the body that ensure sexual reproduction, the essence of which is reduced to fertilization, that is, the fusion of male and female germ cells into a zygote, from which a new organism develops.
The signs by which one sex differs from the other are divided into primary and secondary. The primary sexual characteristics include the genitals, and all the rest are secondary.
In humans, secondary sexual characteristics are body type, voice timbre, the predominance of muscle or adipose tissue, the presence of facial hair, Adam's apple, and mammary glands. So, in women, the pelvis is usually wider than the shoulders, adipose tissue predominates, the mammary glands are expressed, and the voice is high. Men, on the other hand, differ from them in wider shoulders, the predominance of muscle tissue, the presence of hair on the face and Adam's apple, as well as a low voice. Mankind has long been interested in the question of why males and females are born in a ratio of approximately 1:1. An explanation for this was obtained by studying the karyotypes of insects. It turned out that the females of some bugs, grasshoppers and butterflies have one more chromosome than males. In turn, males produce gametes that differ in the number of chromosomes, thereby determining the sex of the offspring in advance. However, it was subsequently found that in most organisms the number of chromosomes in males and females still does not differ, but one of the sexes has a pair of chromosomes that do not fit each other in size, while the other has all paired chromosomes.
A similar difference was also found in the human karyotype: men have two unpaired chromosomes. In shape, these chromosomes at the beginning of division resemble the Latin letters X and Y, and therefore were called X- and Y-chromosomes. The spermatozoa of a man can carry one of these chromosomes and determine the sex of the unborn child. In this regard, human chromosomes and many other organisms are divided into two groups: autosomes and heterochromosomes, or sex chromosomes.
TO autosomes carry chromosomes that are the same for both sexes, while sex chromosomes- these are chromosomes that differ in different sexes and carry information about sexual characteristics. In cases where the sex carries the same sex chromosomes, for example XX, they say that he homozygous or homogametic(forms identical gametes). The other sex, having different sex chromosomes (XY), is called hemizygous(not having a full equivalent of allelic genes), or heterogametic. In humans, most mammals, Drosophila flies and other organisms, the female is homogametic (XX), and the male is heterogametic (XY), while in birds the male is homogametic (ZZ, or XX), and the female is heterogametic (ZW, or XY) .
The X chromosome is a large unequal chromosome that carries over 1500 genes, and many of their mutant alleles cause the development of severe hereditary diseases in humans, such as hemophilia and color blindness. The Y chromosome, in contrast, is very small, containing only about a dozen genes, including specific genes responsible for male development.
The male karyotype is written as ♂46,XY, and the female karyotype is written as ♀46,XX.
Since gametes with sex chromosomes are produced in males with equal probability, the expected sex ratio in the offspring is 1:1, which coincides with the actually observed.
Bees differ from other organisms in that they develop females from fertilized eggs and males from unfertilized ones. Their sex ratio differs from that indicated above, since the process of fertilization is regulated by the uterus, in the genital tract of which spermatozoa are stored from spring for the whole year.
In a number of organisms, sex can be determined in a different way: before fertilization or after it, depending on environmental conditions.
Inheritance of sex-linked traits
Since some genes are located on sex chromosomes that are not the same for members of opposite sexes, the nature of the inheritance of the traits encoded by these genes differs from the general one. This type of inheritance is called criss-cross inheritance because males inherit from their mother and females from their father. Traits determined by genes found on the sex chromosomes are called bonded to the floor. Examples of sex-linked traits are the recessive traits of hemophilia and color blindness, which mostly occur in males because there are no allelic genes on the Y chromosome. Women suffer from such diseases only if they received such symptoms from both their father and mother.
For example, if the mother was a heterozygous carrier of hemophilia, then half of her sons will have impaired blood clotting: X n - normal blood clotting X h- blood incoagulability (hemophilia)
The traits encoded in the genes of the Y chromosome are transmitted purely through the male line and are called hollandic(the presence of a membrane between the toes, increased hairiness of the edge of the auricle).
Gene Interaction
A check of the patterns of independent inheritance on various objects already at the beginning of the 20th century showed that, for example, in a night beauty, when crossing plants with a red and white corolla, the first generation hybrids have pink corollas, while in the second generation there are individuals with red, pink and white flowers in the ratio 1:2:1. This led researchers to the idea that allelic genes can have a certain effect on each other. Subsequently, it was also found that non-allelic genes contribute to the manifestation of signs of other genes or suppress them. These observations became the basis for the concept of the genotype as a system of interacting genes. Currently, the interaction of allelic and non-allelic genes is distinguished.
The interaction of allelic genes includes complete and incomplete dominance, codominance and overdominance. Complete dominance consider all cases of interaction of allelic genes, in which the manifestation of an exclusively dominant trait is observed in the heterozygote, such as, for example, the color and shape of the seed in peas.
incomplete dominance- this is a type of interaction of allelic genes, in which the manifestation of a recessive allele to a greater or lesser extent weakens the manifestation of a dominant one, as in the case of the color of the corolla of the night beauty (white + red = pink) and wool in cattle.
codominance called this type of interaction of allelic genes, in which both alleles appear without weakening the effects of each other. A typical example of codominance is the inheritance of blood groups according to the ABO system (Table 3.2). IV (AB) blood type in humans (genotype - I A I B).
As can be seen from the table, I, II and III blood groups are inherited according to the type of complete dominance, while IV (AB) group (genotype - I A I B) is a case of co-dominance.
overdominance- this is a phenomenon in which in the heterozygous state the dominant trait manifests itself much stronger than in the homozygous state; overdominance is often used in breeding and is thought to be the cause heterosis- phenomena of hybrid power.
A special case of the interaction of allelic genes can be considered the so-called lethal genes, which in the homozygous state lead to the death of the organism most often in the embryonic period. The reason for the death of the offspring is the pleiotropic effect of genes for gray coat color in astrakhan sheep, platinum color in foxes, and the absence of scales in mirror carps. When crossing two individuals heterozygous for these genes, the splitting for the trait under study in the offspring will be 2:1 due to the death of 1/4 of the offspring.
The main types of interaction of non-allelic genes are complementarity, epistasis and polymerization. complementarity- this is a type of interaction of non-allelic genes, in which the presence of at least two dominant alleles of different pairs is necessary for the manifestation of a certain state of a trait. For example, in a pumpkin, when crossing plants with spherical (AAbb) and long (aaBB) fruits in the first generation appear plants with disc-shaped fruits (AaBb).
TO epistasis include such phenomena of the interaction of non-allelic genes, in which one non-allelic gene suppresses the development of a trait of another. For example, in chickens, one dominant gene determines plumage color, while another dominant gene suppresses the development of color, resulting in most chickens having white plumage.
Polymeria called the phenomenon in which non-allelic genes have the same effect on the development of a trait. Thus, most often quantitative signs are encoded. For example, human skin color is determined by at least four pairs of non-allelic genes - the more dominant alleles in the genotype, the darker the skin.
Genotype as an integral system
The genotype is not a mechanical sum of genes, since the possibility of gene manifestation and the form of its manifestation depend on environmental conditions. In this case, the environment means not only the environment, but also the genotypic environment - other genes.
The manifestation of qualitative signs rarely depends on environmental conditions, although if a white-haired area of the body of an ermine rabbit is shaved and an ice pack is applied to it, then black hair will grow in this place over time.
The development of quantitative traits is much more dependent on environmental conditions. For example, if modern varieties of wheat are cultivated without the use of mineral fertilizers, then its yield will differ significantly from the genetically programmed 100 or more centners per hectare.
Thus, only the "abilities" of the organism are recorded in the genotype, but they manifest themselves only in interaction with environmental conditions.
In addition, genes interact with each other and, being in the same genotype, can strongly influence the manifestation of the action of neighboring genes. Thus, for each individual gene, there is a genotypic environment. It is possible that the development of any trait is associated with the action of many genes. In addition, the dependence of several traits on one gene was revealed. For example, in oats, the color of the scales and the length of the seed awn are determined by one gene. In Drosophila, the gene for the white color of the eye simultaneously affects the color of the body and internal organs, the length of the wings, a decrease in fertility, and a decrease in life expectancy. It is possible that each gene is simultaneously the gene of the main action for "its own" trait and a modifier for other traits. Thus, the phenotype is the result of the interaction of the genes of the entire genotype with the environment in the ontogeny of the individual.
In this regard, the famous Russian geneticist M.E. Lobashev defined the genotype as system of interacting genes. This integral system was formed in the process of evolution of the organic world, while only those organisms survived in which the interaction of genes gave the most favorable reaction in ontogenesis.
human genetics
For man as a biological species, the genetic patterns of heredity and variability established for plants and animals are fully valid. At the same time, human genetics, which studies the patterns of heredity and variability in humans at all levels of its organization and existence, occupies a special place among other sections of genetics.
Human genetics is both a fundamental and applied science, since it is engaged in the study of human hereditary diseases, of which more than 4 thousand have already been described. It stimulates the development of modern areas of general and molecular genetics, molecular biology and clinical medicine. Depending on the problematics, human genetics is divided into several areas that have developed into independent sciences: the genetics of normal human traits, medical genetics, the genetics of behavior and intelligence, and human population genetics. In this regard, in our time, a person as a genetic object has been studied almost better than the main model objects of genetics: Drosophila, Arabidopsis, etc.
The biosocial nature of man leaves a significant imprint on research in the field of his genetics due to late puberty and large time gaps between generations, small numbers of offspring, the impossibility of directed crosses for genetic analysis, the absence of pure lines, insufficient accuracy of registration of hereditary traits and small pedigrees, the impossibility of creating the same and strictly controlled conditions for the development of offspring from different marriages, a relatively large number of poorly differing chromosomes, and the impossibility of experimentally obtaining mutations.
Methods for studying human genetics
The methods used in human genetics do not fundamentally differ from those generally accepted for other objects - this genealogical, twin, cytogenetic, dermatoglyphic, molecular biological And population-statistical methods, somatic cell hybridization method And modeling method. Their use in human genetics takes into account the specifics of a person as a genetic object.
twin method helps to determine the contribution of heredity and the influence of environmental conditions on the manifestation of a trait based on the analysis of the coincidence of these traits in identical and fraternal twins. So, most identical twins have the same blood types, eye and hair color, as well as a number of other signs, while both types of twins get measles at the same time.
Dermatoglyphic method is based on the study of the individual characteristics of the skin patterns of the fingers (dactyloscopy), palms and feet. Based on these features, it often allows timely detection of hereditary diseases, in particular chromosomal abnormalities, such as Down syndrome, Shereshevsky-Turner syndrome, etc.
genealogical method- this is a method of compiling pedigrees, with the help of which the nature of the inheritance of the studied traits, including hereditary diseases, is determined, and the birth of offspring with the corresponding traits is predicted. He made it possible to reveal the hereditary nature of such diseases as hemophilia, color blindness, Huntington's chorea, and others even before the discovery of the main patterns of heredity. When compiling pedigrees, records are kept about each of the family members and take into account the degree of relationship between them. Further, based on the data obtained, using special symbols, a family tree is built (Fig. 3.13).
The genealogical method can be used on one family if there is information about a sufficient number of direct relatives of the person whose pedigree is being compiled - proband,- on the paternal and maternal lines, otherwise they collect information about several families in which this feature is manifested. The genealogical method allows you to establish not only the heritability of the trait, but also the nature of inheritance: dominant or recessive, autosomal or sex-linked, etc. Thus, according to the portraits of the Austrian Habsburg monarchs, the inheritance of prognathia (a strongly protruding lower lip) and "royal hemophilia" was established among the descendants of the British Queen Victoria (Fig. 3.14).
Solution of genetic problems. Drawing up crossbreeding schemes
All variety of genetic problems can be reduced to three types:
1. Calculation problems.
2. Tasks for determining the genotype.
3. Tasks to establish the type of inheritance of a trait.
feature calculation problems is the availability of information about the inheritance of the trait and the phenotypes of the parents, by which it is easy to establish the genotypes of the parents. They need to establish the genotypes and phenotypes of the offspring.
