The organism as a biological system: features, functions and a brief theory

breeding method

features

examples of organisms

cell division in two

the body of the parent cell is divided by mitosis into two parts, each of which gives rise to full-fledged cells

prokaryotes, unicellular eukaryotes (amoeba)

multiple cell division

The body of the original cell divides mitotically into several parts, each of which becomes a new cell

Unicellular eukaryotes (flagellates, sporozoans)

budding

A tubercle containing a nucleus is first formed on the mother's cell. Kidney grows, reaches maternal size, detaches

Unicellular eukaryotes, some ciliates, yeast

sporulation

Spore is a special cage, covered with a dense membrane that protects against external influences

Spore plants; some protozoa

vegetative reproduction:

An increase in the number of individuals of this species occurs by the separation of the viable parts of the vegetative body of the organism

Plants, animals

In plants

Formation of buds, stem and root tubers, bulbs, rhizomes

Liliaceae, nightshade, gooseberry, etc.

In animals

Ordered and unordered division

Intestinal, starfish, annelids

features

prezygous

the formation of gametes (gametogenesis), the accumulation of ribosomal and messenger RNA, different parts of the cytoplasm acquire differences in chemical composition.

embryonic period

zygote (unicellular stage of development of a multicellular organism)

contains yolk grains, mitochondria, pigments, cytoplasm moves, pronounced bilateral symmetry (bilateral). A number of animal species begin to synthesize protein and new RNA

splitting up

cleavage grooves are formed, which divide the cell in half - into 2 blastomeres (2,4,8,16,32,64, etc.). As a result of a series of successive cleavages, a group of cells closely adjacent to each other is formed. The embryo resembles a raspberry berry. It was named morula.

blastulation

the final stage of egg crushing. In the lancelet, blastula is formed when the embryo reaches 128 cells. Blastula is in the form of a bubble with a wall of one layer of cells called blastoderm.

gastrulation

complex movement of embryonic material with the formation of 2 or 3 layers of the body of the embryo (germ layers): ectoderm, endoderm and mesoderm. The development of sponges and coelenterates ends at the stage of two germ layers. All other organisms that are higher on the evolutionary ladder develop three germ layers.

histogenesis and organogenesis

the formation of tissues and organs occurs

causes of manifestation

value

Non-hereditary (modification variability)

a change in environmental conditions, as a result of which the organism changes within the normal range of the reaction given by the genotype

adaptation - adaptation to given environmental conditions, survival, preservation of offspring.

white cabbage in hot climates does not form a head of cabbage; breeds of horses and cows brought to the mountains become stunted

Hereditary (genotypic)

Mutational

influence of external and internal mutagenic factors, resulting in a change in genes and chromosomes

material of natural and artificial selection, since mutations can be useful, harmful and indifferent, dominant and recessive

reproductive isolation\u003e new species, genus\u003e microevolution.

Combinative

occurs spontaneously within the population during crossing, when new combinations of genes appear in the offspring.

the spread of new hereditary changes that serve as material for selection.

the appearance of pink flowers when crossing white-flowered and red-flowered primroses.

Relative (correlative)

arises as a result of the properties of genes to influence the formation of not one, but two or more signs

the constancy of interrelated signs, the integrity of the organism as a system

long-legged animals have a long neck.

aromorphosis

idioadaptation

general degeneration

hypergenesis

The emergence of electron transport chains (which provided the possibility of photosynthesis and aerobic respiration)

Galapagos finches (different types of beaks)

Head disappearance in bivalve molluscs

The appearance of histone proteins and the nuclear envelope (which provided the possibility of mitosis, meiosis and sexual reproduction)

Dogs have non-retractable claws to speed up running, the presence of predatory teeth, a decrease in body temperature through increased mouth breathing (no sweat glands)

Pork tapeworm has a "loss" of the digestive system.

The emergence of germ layers in animals and differentiated tissues in plants (which led to the formation of organ systems).

In ladybirds, salamanders have a warning coloration.

Loss of vision in moles, proteus, deep-sea

The appearance of the axial skeleton - chord

Introduction 2

1. The organism as a single self-developing and self-regulating biological system 4

2. The external environment and its impact on the body and human life 6

3. Means physical cultureproviding resistance to mental and physical performance 8

4. Motor function and an increase in the level of adaptation and resistance of the human body to different conditions external environment 13

Conclusion 16

References 19

Introduction

Biomedical and pedagogical sciences deal with man as a creature not only biological, but also social. Sociality is the specific essence of a person, which does not abolish his biological substance, because the biological principle of a person is a necessary condition for the formation and manifestation of a social way of life. Meanwhile, it is not organisms that are making history, changing the living and inanimate world, creating and destroying, setting world and Olympic records, but people, human personalities. Thus, the socio-biological foundations of physical culture are the principles of interaction of social and biological laws in the process of mastering the values \u200b\u200bof physical culture by a person.

The natural-scientific foundations of physical culture are a complex of medical and biological sciences (anatomy, physiology, biology, biochemistry, hygiene, etc.). Anatomy and physiology are the most important biological sciences about the structure and functions of the human body. Man obeys biological laws inherent in all living things. 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 of life and social relationships. Labor and the influence of the social environment in the process of human development have influenced the biological characteristics of the body of a modern person and his environment. The study of human organs and interfunctional systems is based on the principle of integrity and unity of the organism with the external natural and social environment.

The body is a harmonious single self-regulating and self-developing biological system, the functional activity of which is due to 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 impact on external natural and social conditions that determine the state of human health, their performance, life expectancy and fertility (reproductive capacity).

Without knowledge about the structure of the human body, about the regularities of the functioning of individual organs and systems of the body, about the peculiarities of the complex processes of its vital activity, it is impossible to organize the process of forming a healthy lifestyle and physical training of the population, including students. The achievements of biomedical sciences underlie the pedagogical principles and methods of the educational and training process, the theory and methods of physical education and sports training.

All these issues require further consideration and study, which is the purpose of this work, the tasks of which include systematization, accumulation and consolidation of knowledge about the socio-biological foundations of physical culture and sports.

1. The organism as a single self-developing and self-regulating biological system

The development of the organism is carried out in all periods of its life - from the moment of conception to death. This development is called individual, or development in ontogeny. At the same time, two periods are distinguished: intrauterine (from the moment of conception to before birth) and extrauterine (after birth).

Each born person inherits from his parents congenital, genetically determined traits and characteristics, which largely determine individual development in the process of his later life.

Once after birth, figuratively speaking, in an autonomous regime, the child grows rapidly, the weight, length and surface area of \u200b\u200bhis body increase. Human growth continues until about 20 years of age. Moreover, in girls, the highest growth rate is observed in the period from 10 to 13, and in boys from 12 to 16 years. The increase in body weight occurs almost in parallel with the 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 morphological and functional development of the body in children and adolescents. This phenomenon is called acceleration (lat.accelera - acceleration), it is associated not only with the acceleration of growth and development of the body in general, but also with an earlier onset of puberty, accelerated development of sensory (lat.wepre - feeling), motor coordination and mental functions ... Therefore, the boundaries between age periods are rather arbitrary, and this is due to significant individual differences, in which the “physiological” age and the “passport” age do not always coincide.

As a rule, adolescence (16 - 21 years old) is associated with a period of maturation, when all organs, their systems and apparatuses reach their morphological and functional maturity. Mature age (22 - 60 years) is characterized by minor changes in the structure of the body, and the functional capabilities of this rather long period of life are largely determined by the characteristics of the lifestyle, nutrition, and motor activity. Elderly age (61 - 74 years old) and senile (75 years old 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 physical activity during life significantly slows down the aging process ...

The vital activity of the organism is based on the process of automatically maintaining vital factors at the required level, any deviation from which leads to the immediate mobilization of mechanisms that restore this level (homeostasis).

Homeostasis is a set of reactions that maintain or restore a relatively dynamic constancy of the internal environment and some physiological functions of the human body (blood circulation, metabolism, thermoregulation, etc.). This process is provided by a complex system of coordinated adaptive mechanisms aimed at eliminating or limiting factors affecting the body from both the external and internal environment. They allow maintaining the constancy of the composition, physicochemical and biological properties of the internal environment, despite changes in the external world and physiological shifts that occur during the life of the organism. In a normal state, fluctuations in physiological and biochemical constants occur within narrow homeostatic boundaries, and the cells of the body live in a relatively constant environment, since they are washed by blood, lymph and tissue fluid. The constancy of the physicochemical composition is maintained due to the self-regulation of metabolism, blood circulation, digestion, respiration, excretion and other physiological processes.

An organism is a complex biological system. All its organs are interconnected and interact. Disruption of the activity of one organ leads to disruption of the activity of others.

A huge number of cells, each of which performs its own functions inherent only to it in the general structural and functional system of the body, are supplied with nutrients and the necessary amount of oxygen in order to carry out vital processes of energy production, excretion of decay products, ensuring various biochemical reactions of vital activity, etc. .d. These processes occur due to regulatory mechanisms that carry out their activity through the nervous, circulatory, respiratory, endocrine and other systems of the body.

2. The external environment and its impact on the body and human life

External environment . A person is affected by various environmental factors. When studying the various types of its activities, one should not do without taking into account the influence of natural factors (barometric pressure, gas composition and air humidity, ambient temperature, solar radiation - the so-called physical environment), biological factors of the plant and animal environment, as well as factors of the social environment with the results of household, economic, industrial and creative human activities.

From the external environment, the body receives substances necessary for its life and development, as well as stimuli (useful and harmful) that violate the constancy of the internal environment. The body, through the interaction of functional systems, in every possible way seeks to maintain the necessary constancy of its internal: environment.

The activity of all organs and their systems in the whole organism is characterized by certain indicators that have certain "ranges of fluctuations. Some constants are stable and rather rigid (for example, blood pH 7.36 - 7.40, body temperature - within 35 -: 42" 0), others and normally differ by significant fluctuations (for example, the stroke volume of the heart - the amount of blood ejected in one contraction - 50 - 200 cm "). Lower vertebrates, in which the regulation of indicators characterizing the state of the internal environment is imperfect, are in For example, a frog, not possessing a mechanism that regulates the constancy of body temperature, duplicates the temperature of the external environment so much that in winter all life processes in it are inhibited, and in summer, being far from water, it dries up and dies. higher animals, including man, sort of placed themselves in a greenhouse, creating their own stable internal environment and providing thus, relative independence from the external environment.

Natural socio-ecological factors and their impact on the body.

Natural and socio-biological logical factors affecting the human body are inextricably linked with environmental issues.

Ecology (Greek, oikos - house, dwelling, homeland + logos - concept, doctrine) is both a field of knowledge, a part of biology, an academic discipline, and a complex science. Ecology examines the relationship of organisms with each other and with inanimate components of nature: the Earth (its biosphere). Human ecology studies the laws of human interaction with nature, the problems of maintaining and strengthening health. Man depends on environmental conditions in the same way that nature depends on man. Meanwhile, the impact of industrial activities on the environment (pollution of the atmosphere, soil, water bodies with industrial waste, deforestation, increased radiation as a result of accidents and violations of technology) endangers the existence of man himself. For example, in large cities, the natural environment is significantly deteriorating, the rhythm of life, the psychoemotional situation of work, life, recreation are disrupted, the climate is changing. In cities, the intensity of solar radiation is 15 - 20% lower than in the surrounding area, but the average annual temperature is 1 - 2 "0 higher, daily and seasonal fluctuations are less significant, atmospheric pressure is lower, polluted air. All these changes have an extremely adverse effect on physical and mental health of a person About 80M diseases of a modern person are the result of the deterioration of the ecological situation on the planet.Environmental problems are directly related to the process of organizing and conducting systematic physical exercises and sports, as well as to the conditions in which they occur.

3.2. Reproduction of organisms, its meaning. Reproduction methods, 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. Ontogenesis and its inherent patterns. Specialization of cells, formation of tissues, organs. Embryonic and postembryonic development of organisms. Life cycles and alternation of generations. The reasons for the violation of the development of organisms.

3.5. Regularities of heredity, their cytological foundations. Mono- and dihybrid crossing. The patterns of inheritance established by G. Mendel. Linked inheritance of traits, gene linkage disorder. T. Morgan's laws. Chromosomal theory of heredity. Genetics of sex. Inheritance of sex-linked traits. Genotype as an integral system. Development of knowledge about the genotype. The human genome. Interaction of genes. Solving genetic problems. Drawing up crossing schemes. G. Mendel's laws and their cytological foundations.

3.6. Variability of traits in organisms: modification, mutational, combinative. Types of mutations and their causes. The significance 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 effect of mutagens, alcohol, drugs, nicotine on the genetic apparatus of the cell. Protection of the environment from contamination 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. Hereditary human diseases, their causes, prevention.

3.7.1. Mutagens, mutagenesis.

3.8. Breeding, its tasks and practical significance. The teachings of N.I. Vavilov on the centers of diversity and origin of cultivated plants. The law of homologous series in hereditary variation. Methods for breeding new varieties of plants, animal breeds, strains of microorganisms. The value of genetics for breeding. Biological bases of cultivation of cultivated plants and domestic animals.

3.8.1. Genetics and breeding.

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, microbiological industry, preservation of the planet's gene pool. Ethical aspects of the development of some research in biotechnology (human cloning, directed genome changes).

3.9.1. Cellular and genetic engineering. Biotechnology.

Variety of organisms: unicellular and multicellular; autotrophs, heterotrophs.

Single-celled and multicellular organisms

The extraordinary variety of living things on the planet makes it necessary to find various criteria for their classification. So, they are classified as cellular and non-cellular forms of life, since cells are a 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 similar morphologically and are 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 organismic levels of organization. The vast majority of bacteria, part of animals (protozoa), plants (some algae) and fungi are unicellular. Some taxonomists even suggest separating unicellular organisms into a special kingdom - protists.

Colonial They call organisms in which, in the process of asexual reproduction, daughter individuals remain connected to the mother's 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, pandorin and eudorin algae. Colonial organisms, apparently, were an intermediate link in the process of the emergence of multicellular organisms.

Multicellular organisms, no doubt, have a higher level of organization than unicellular organisms, since their body is formed by many cells. Unlike colonial organisms, which can also have more than one cell, in multicellular organisms, cells specialize in performing various functions, which is reflected in their structure. The payment for this specialization is the loss of their cells' ability to independently exist, and often to reproduce their own kind. The division of an individual cell leads to the growth of a multicellular organism, but not to its reproduction. Ontogenesis of multicellular organisms is characterized by the process of cleavage of a fertilized egg into many blastomere cells, from which an organism with differentiated tissues and organs is subsequently formed. Multicellular organisms are usually larger than unicellular organisms. The increase in body size 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 organizational advantages over unicellular organisms and represent a qualitative leap in the evolutionary process. Few bacteria, most plants, animals and fungi are multicellular.

Autotrophs and heterotrophs

According to the way of feeding, all organisms are divided into autotrophs and heterotrophs. Autotrophs are able to independently synthesize organic substances from inorganic ones, and 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 are 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. Saprotrophs include many fungi and bacteria, as well as some plants and animals.

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 incapable of manifesting 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), but 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).

Nowadays, about 1000 viruses are already known, which are classified according to objects of damage, shape and other signs, but the most common classification is according to the characteristics of 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 conventionally divided into simple and complex. Simple viruses consist of a nucleic acid and a protein coat - 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. Viruses of bacteria - bacteriophages (from the Greek bacterion - bacillus and phagos - devourer) have the most complex structure, in which a head and an appendix, 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 cover and a hollow core hidden inside it are distinguished. In the lower part of the rod there is a special plate with spines and filaments 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), therefore 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 - double-stranded.

Since viruses are deprived of organelles of movement, infection occurs through direct contact of the virus with the cell. This mainly occurs through airborne droplets (influenza), through the digestive system (hepatitis), blood (HIV) or a carrier (encephalitis virus).

Viruses can enter the cell directly by accident, with a liquid 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 - 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 that 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 host cell surface, bacteriophages "pierce" it with their core and inject 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 pathway and the penetration of the virus through the plasmodesmata are possible.

After penetration into the cell, the virus is “undressed”, that is, the capsid is lost. 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 DNA is synthesized on RNA first, which is then inserted into the genome of the host cell (HIV), or it can be directly protein synthesis occurs (influenza virus). Reproduction of viral nucleic acid and synthesis of capsid proteins using the protein-synthesizing apparatus of the cell are essential components of viral infection, after which the self-assembly of viral particles and their exit from the cell occur. In some cases, viral particles leave the cell, gradually budding from it, while in other cases a microexplosion occurs, accompanied by cell death.

Viruses not only inhibit the synthesis of their own macromolecules in the cell, but can also cause damage to cellular structures, especially during a massive exit from the cell. This leads, for example, to the mass death of industrial cultures of lactic acid bacteria in the case 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 penetrate into a cell often quickly suppress its repair systems and cause death, another scenario is also possible - the activation of the body's defenses, which is associated with the synthesis of antiviral proteins, for example, interferon and immunoglobulins. At the same time, the reproduction of the virus is interrupted, new viral particles are not formed, and the remains of the virus are removed from the cell.

Viruses cause numerous diseases in humans, animals and plants. In plants it is a mosaic of tobacco and tulips, in humans - influenza, rubella, measles, AIDS, etc. In the history of mankind, viruses of smallpox, "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 a variety of 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 ensuring the so-called horizontal gene transfer, the formation of mutations and, ultimately, the supply of material for the evolutionary process.

Nowadays, 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.

Disease AIDS and HIV infection

HIV (Human Immunodeficiency Virus) was discovered only in the early 80s of the XX century, however, the rate of spread of the disease it causes and the impossibility of cure at this stage in the development of medicine force to pay increased attention to it. In 2008 F. Barre-Sinoussi and L. Montagnier were awarded the Nobel Prize in Physiology and Medicine for their HIV research.

HIV is a complex RNA virus that primarily infects T4 lymphocytes, which coordinate the entire immune system (Fig. 3.3). On the RNA of the virus, DNA is synthesized with the help of the enzyme RNA-dependent DNA polymerase (reverse transcriptase), which is integrated into the genome of the host cell, turns into a provirus, and "hides" indefinitely. Subsequently, reading of information about viral RNA and proteins, which are collected in viral particles and almost simultaneously leave it, begins from this DNA site, dooming 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, however, no matter how long this period lasts, the last stage, which is called acquired immunodeficiency syndrome, or AIDS, still occurs.

The disease is characterized by a decrease and then a complete loss of the body's immunity to all pathogens. The 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, etc.), severe pneumonia and other AIDS-associated diseases.

HIV is transmitted sexually, through blood and other body fluids, but not through handshakes and household items. At first, in our country, HIV infection was more often associated with indiscriminate ^ sexual contacts, especially homosexual ones, injection drug addiction, transfusion of infected 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, promiscuity in sexual intercourse and refusal to use drugs.

Measures to prevent the spread of viral diseases

The main means of preventing viral diseases in humans is wearing gauze bandages in contact with sick respiratory diseases, washing hands, vegetables and fruits, dressing the habitats of vectors of viral diseases, vaccination against tick-borne encephalitis, sterilization of medical instruments in hospitals, etc. To avoid infection HIV should also stop using alcohol, drugs, have a single sexual partner, use personal protective equipment during sexual intercourse, etc.

Viroids

Viroids (from the Latin virus - poison and Greek eidos - form, species) are the smallest causative agents of plant diseases, which contain only low molecular weight RNA.

Their nucleic acid, probably, does not encode its own proteins, but only reproduces in the cells of the host plant using its enzyme systems. Often, it can also cut the host cell's DNA into several pieces, thereby condemning the cell and the plant as a whole to death. For example, a few years ago, viroids caused the death of millions of coconut trees in the Philippines.

Prions

Prions (abbreviated English proteinaceous infectious and -on) are small infectious agents of proteinaceous nature, in the form of a filament or crystal.

Proteins of the same composition are found in a normal cell, but prions have a special tertiary structure. Entering the body with food, they help the corresponding "normal" proteins acquire the structure characteristic of prions themselves, which leads to the accumulation of "abnormal" proteins and a deficiency of normal ones. Naturally, this causes dysfunctions 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 meaning. Reproduction methods, 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 lifespan of a single individual is finite, therefore, the transmission of hereditary information from one generation to the next during reproduction ensures the survival of this type of organism for long periods of time. Thus, reproduction ensures the continuity and continuity 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 survive to the stage of development at which they themselves will be able to give offspring, since they can be destroyed by predators, die from diseases and natural disasters, such as fires. floods, etc.

Reproduction methods, 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, takes place, only one parent organism takes part in it. Asexual reproduction is based on mitotic cell division.

Depending on how many cells of the maternal organism give rise to a new individual, asexual reproduction is subdivided into asexual and vegetative. With asexual reproduction itself, a daughter individual develops from a single cell of the mother's body, and with vegetative reproduction, from a group of cells or a whole organ.

In nature, there are four main types of proper asexual reproduction: binary fission, multiple fission, sporulation and simple budding.

Binary division is essentially a simple mitotic division of a unicellular maternal organism, in which the nucleus is divided first, and then the cytoplasm. It is typical for various representatives of the plant and animal kingdoms, for example, the amoeba proteus and ciliates-shoes.

Multiple division, or schizogony, is preceded by repeated division of the nucleus, after which the cytoplasm is divided into the corresponding number of fragments. This type of asexual reproduction is found in unicellular animals - sporozoans, for example, in the malaria plasmodium.

In many plants and fungi, in the life cycle, spores are formed - single-celled specialized formations containing a supply of nutrients and covered with a dense protective shell. Spores are carried by wind and water, and, if conditions are favorable, germinate, giving rise to a new multicellular organism.

A typical example of budding as a kind of proper asexual reproduction 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 detached. Thus, the ability of the mother cell to further divide 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 hydra buds, a protrusion of the body wall is formed, which gradually increases in size, at the front end, a mouth opening, surrounded by tentacles, breaks out. It ends with the formation of a small hydra, which is then separated from the mother's body. 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 from each develop full-fledged individuals (jellyfish, sea anemones, flat and annelid worms, echinoderms).

With polyembryony, the embryo, which has formed as a result of fertilization, is divided into several embryos. This phenomenon occurs regularly in armadillos, but it can also occur in humans in the case of identical twins.

The most highly developed ability for vegetative reproduction is in plants, in which tubers, bulbs, rhizomes, root suckers, whiskers and even brood buds can give rise to a new organism.

Asexual reproduction requires only one parent, which saves the time and energy needed to find a mate. In addition, new individuals can arise from each fragment of the mother's body, which also saves 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 - clones are formed, which can be considered an advantage provided that the environmental conditions remain constant.

However, due to the fact that the only source of genetic variability is random mutations, the almost complete absence of variability among the offspring reduces their adaptability to new environmental conditions during dispersal and, as a consequence, they die in much larger numbers than during sexual reproduction.

Sexual reproduction - a method of reproduction, in which the formation and fusion of sex cells, or gametes, occurs into one cell - a zygote, from which a new organism develops.

If during sexual reproduction somatic cells with a diploid set of chromosomes merged (in humans 2n \u003d 46), then already in the second generation the cells of the new organism would already contain a tetraploid set (in humans 4n \u003d 92), in the third - an octaploid set, etc. ...

However, the size of a eukaryotic cell is not infinite, they should fluctuate within 10-100 microns, since with a smaller cell size, 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 and carbon dioxide will be disrupted. 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 cell volume, 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 provided by the process of meiotic cell division.

The decrease in the number of chromosomes should also be strictly ordered and equivalent, because if a new organism does not have complete pairs of chromosomes with their general normal number, then it will either not be viable, or it 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 generally the constancy of the karyotype.

Parthenogenesis and conjugation are special forms of sexual reproduction. In parthenogenesis, or virgin development, a new organism develops from an unfertilized egg, such as in daphnia, honey bees, and some rock lizards. Sometimes this process is stimulated by the introduction of sperm from other organisms.

In the process of conjugation, which is characteristic, 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 germ 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 annelid worms, gastropods.

Plants in which male and female flowers or other dissimilar genital organs 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 in offspring, which is based on meiosis and recombination of parental genes during fertilization. The most successful combinations of genes ensure the best adaptation of the offspring 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, substance and energy are used ineffectively 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, energy has to be expended on providing other conditions. For example, plants form flowers and produce nectar to attract animals, which carry pollen to the female parts of other flowers, and animals spend a lot of time and energy looking for mates and courtship. Then you have to spend a lot of energy on caring for the offspring, since during sexual reproduction the offspring are often so small at first that many of them die from predators, hunger, or simply because of unfavorable conditions. Consequently, with 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 for breeding new varieties of plants and animal breeds, preserving economically valuable traits, and also rapidly increasing the number of individuals.

With 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 taking the 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 rapidly multiply plant varieties with valuable traits, for example, potatoes resistant to the leaf roll virus, 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 plant somatic cells, which cannot be crossed in any other way.

Crossing plants of various varieties makes it possible to obtain organisms with new combinations of economically valuable traits. To do this, use pollination with pollen of plants of the same or another species and even genus. This phenomenon is called distant hybridization.

Since higher animals lack the ability for natural asexual reproduction, the main way of their reproduction is sexual. For this, the crossing of individuals of both the same species (breed) and interspecific hybridization are used, while such well-known hybrids as mule and hinny are obtained, depending on which species were taken as maternal - donkey and horse. However, interspecific hybrids are often sterile, that is, unable to produce offspring, so each time they must be re-hatched.

Artificial parthenogenesis is also used for breeding farm animals. The outstanding Russian geneticist BL Astaurov, raising the temperature, caused a greater output of silkworm females, which weave cocoons from a thinner and more valuable thread than males.

Cloning can also be considered asexual reproduction, since the nucleus of a somatic cell is used, 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 is the process of fusion of male and female germ cells to form a zygote.

In the process of fertilization, first there is recognition and physical contact of male and female gametes, then the fusion of their cytoplasm, and only at the last stage is the fusion of hereditary material. Fertilization allows you to restore the diploid set of chromosomes, reduced during the formation of germ cells.

Most often in nature, fertilization by male germ cells of another organism occurs, but in a number of cases, the penetration of its own spermatozoa is also possible - self-fertilization. From an evolutionary point of view, self-fertilization is less profitable, since the likelihood of new combinations of genes is minimal. Therefore, even in most hermaphrodite organisms, cross fertilization occurs. This process is inherent in both plants and animals, however, in its course, the aforementioned organisms have a number of differences.

So, in flowering plants, fertilization is preceded by pollination - transfer of pollen containing male germ 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 subsequently storing 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 the sperm in space.

When breeding 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 viability in general decreases. In addition, soybeans and many other cultivated plants are self-pollinated, so human intervention is needed to develop new varieties. Difficulties can also arise in the process of fertilization itself, since some plants and animals may have genes for sterility.

In plants for breeding purposes, 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 the pollinated flowers are covered with insulating caps to avoid pollination with pollen from other plants. In some cases, artificial pollination is performed to increase yields, since seeds and fruits do not develop from the ovaries of unpolished flowers. This technique was previously practiced in sunflower crops.

With distant hybridization, especially if plants differ in the number of chromosomes, natural fertilization becomes either completely impossible, or already with the first cell division, a violation of chromosome separation occurs and the body dies. In this case, fertilization is carried out in artificial conditions, and at the beginning of division, the cell is treated with colchicine, a substance that destroys the spindle of division, while the chromosomes are scattered throughout the cell, and then a new nucleus is formed with a doubled number of chromosomes, and with subsequent divisions such problems do not arise. Thus, a rare cabbage hybrid of GD Karpechenko and triticale was created - a high-yielding hybrid of wheat and rye.

In the main species of farm animals, there are even more obstacles to fertilization than in plants, which forces humans to take drastic measures. Artificial insemination is used mainly in the breeding of cattle of valuable breeds, when it is necessary to get as many offspring as possible from one producer. In these cases, semen is collected, mixed with water, placed in ampoules, and then, as necessary, injected into the female genital tract. In fish farms, during artificial insemination in fish, the sperm of males obtained from milk is mixed with caviar in special containers. Juveniles raised in special cages are then released into natural reservoirs and restore the population, for example, of sturgeon 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

In animals, external and internal fertilization are distinguished. When external fertilizationfemale and male reproductive cells are removed to the outside, where the process of their fusion occurs, as, for example, in annelids, bivalve molluscs, skullless, most fish and many amphibians. Despite the fact that it does not require the rapprochement of the breeding individuals, in mobile animals, not only their rapprochement is possible, but also accumulation, as during spawning of fish.

Internal fertilization associated with the introduction of male reproductive products into the female genital tract, and an already fertilized egg is excreted. It often has dense membranes that prevent damage and penetration of the next sperm. Internal fertilization is typical for the overwhelming majority of land animals, for example, for flat and round worms, many arthropods and gastropods, reptiles, birds and mammals, as well as for a number of amphibians. It also occurs 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 a transition from external to internal.

Both external and internal fertilization have their own advantages and disadvantages. So, with external fertilization, the sex 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 sedentary animals as bivalve molluscs and skullless ones. With internal fertilization, the loss of gametes is certainly much less, but at the same time, matter and energy are spent on finding a partner, and the offspring that have been born are often too small and weak and require long-term parental care.

3.3. Ontogenesis and its inherent patterns. Specialization of cells, formation of tissues, organs. Embryonic and postembryonic development of organisms. Life cycles and alternation of generations. The reasons for the violation of the development of organisms.

Ontogenesis and its inherent patterns

Ontogenesis (from the Greek. ontos - being and genesis - occurrence, origin) is the process of individual development of an organism from inception 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 emergence of a zygote as a result of fertilization of an egg by a sperm, although during parthenogenesis, a zygote as such is not formed. In the process of ontogenesis, growth, differentiation and integration of parts of the developing organism take place. Differentiation (from lat. differentio - difference) is called the process of occurrence of differences between homogeneous tissues and organs, their changes during the development of an individual, leading to the formation of specialized tissues and organs.

Patterns of ontogenesis are the subject of study embryology (from the Greek. embryo - the embryo and logos - word, science). A significant contribution to its development was made by the Russian scientists K. Baer (1792-1876), who discovered the mammalian ovum and laid 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 characteristic only of 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 ontogeny is determined by genetic programs that have been entrenched in the process of evolution, that is, ontogeny is a brief repetition of the historical development of a given species, or phylogeny.

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. So, any disruptions in the development process can lead to the interruption of the ontogenetic process at any of the stages, as it often happens 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 an individual and proceeds unidirectionally.

Embryonic and postembryonic development of organisms

Periods of ontogenesis

There are several periodizations 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 continues from birth to death of the organism. Sometimes they distinguish and the pro-embryonic period, or progenesis, which includes gametogenesis and fertilization.

Embryonic development, or embryogenesis, in animals and humans are divided into a number of stages: fragmentation, gastrulation, histogenesis and organogenesis, as well as the period of the 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, and so on. 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 the size of daughter cells should increase. This process is similar to ice picking, but it is not chaotic, but strictly ordered. For example, in humans, this cleavage is bilateral, that is, bilaterally symmetric. As a result of cleavage and subsequent separation of cells, 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 blastocele.

Gastrulation the process of formation of a two- or three-layer embryo is called - gastrula(from the Greek. gaster - stomach), which occurs immediately after the formation of 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 blastula walls. In addition to two or three layers of cells, gastrula also has a primary mouth - blastopore.

The gastrula cell layers are called germ layers. There are three germ layers: ectoderm, mesoderm and endoderm. Ectoderm (from the Greek. ectos - outside, outside and dermis - skin) is the outer germ layer, mesoderm (from the Greek. mesos - medium, intermediate) - medium, and endoderm (from the 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 clones of it, since they are formed as a result of mitotic division, the process of gastrulation 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 subsequently 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 by the hormonal background. For example, if a fragment is transplanted from one frog embryo to another, on which the notochord develops, then this will cause the formation of an embryo of the nervous system in the wrong place, and a kind of double embryo will begin to form. This phenomenon is called embryonic induction.

Histogenesis call the process of formation of mature tissues inherent in an adult body, and organogenesis - the process of organ formation.

In the process of histo- and organogenesis, the epithelium of the skin and its derivatives (hair, nails, claws, feathers), the epithelium of the oral cavity and enamel of the teeth, the rectum, the nervous system, the sense organs, the gills, etc. are formed from the ectoderm. The derivatives of the endoderm are the intestines and associated 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 cartilaginous 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 - neurulae (novolat. neurula, reduce, from the Greek. neuron - nerve). This process is also accompanied by the laying of a complex of axial organs, for example, the chord.

After the course of organogenesis, a period begins a 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 appear that are not useful in subsequent development, for example, the placenta, umbilical cord, etc.

Postembryonic development of animals according to their reproductive capacity is divided into pre-reproductive (juvenile), reproductive and post-reproductive periods.

Juvenile period lasts from birth to puberty, it is characterized by intense growth and development of the body.

The growth of an 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 closed growth occurs only during certain periods of life, mainly before puberty. It is typical for most animals. For example, a person grows mainly up to 13-15 years old, although the final formation of the body occurs before 25 years. Unlimited, or open growth continues throughout the life of the individual, as in plants and some fish. There is also periodic and non-periodic growth.

The growth processes are controlled by the endocrine, or hormonal system: in humans, the release of growth hormone contributes to an increase in the linear size of the body, while gonadotropic hormones suppress it to a significant extent. Similar mechanisms have been discovered in insects, which have a special juvenile hormone and a molting hormone.

In flowering plants, embryonic development proceeds after double fertilization, in which one sperm fertilizes the egg, and the second - the central cell. An embryo is formed from the zygote, which undergoes a series of divisions. After the first division, the actual embryo is formed from one cell, and from the second - suspensions, through which the embryo is supplied with nutrients. The central cell gives rise to the triploid endosperm, which contains nutrients for the development of the embryo (Figure 3.7).

The embryonic and postembryonic development of seed plants are often separated in time, as they require certain conditions for germination. The postembryonic period in plants is divided into vegetative, generative and aging periods. In the vegetative period, the biomass of the plant increases; in the generative period, they acquire the ability to reproduce sexually (in seed, 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 passing which the organism 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 the diploid set predominates in higher plants and animals, and vice versa in lower ones.

Life cycles can be simple or complex. Unlike a simple life cycle, in a complex sexual reproduction alternates with parthenogenetic and asexual. For example, the Daphnia crustaceans, which give asexual generations during the summer, reproduce sexually in the fall. 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 manifestation of all genes, while in the second, some genes are not found.

Causes of developmental disorders of organisms

The ability to self-regulate and to withstand the harmful effects 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 membranes or by the mother's organism itself. It is either supplied with special nourishing tissue, or it receives nutrients directly from the mother's body. Nevertheless, changes in external conditions can accelerate or slow down the development of the embryo and even cause the occurrence of various disorders.

Factors causing abnormalities 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 refers primarily to ionizing radiation, which provokes numerous fetal mutations that may be incompatible with life.

Chemical teratogens are heavy metals, benzopyrene emitted from cars and industrial plants, phenols, a number of drugs, alcohol, drugs and nicotine.

A particularly harmful effect on the development of a human embryo is exerted by his parents' use of alcohol, drugs, smoking tobacco, since alcohol and nicotine inhibit cellular respiration. An insufficient supply of oxygen to the embryo leads to the fact that fewer cells are formed in the forming organs, the organs are underdeveloped. Nervous tissue is especially sensitive to a lack of oxygen. The use of alcohol, drugs by the expectant mother, tobacco smoking, and 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 the properties of organisms. Basic genetic concepts.

Genetics, its tasks

The advances in natural science and cell biology in the 18th-19th centuries allowed a number of scientists to make assumptions 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 H. de Vries in 1889, which assumed the existence in the cell nucleus of certain "pangens" that determine the hereditary inclinations of the organism, and the release into the protoplasm of only those of them that determine the type of cell, could not change the situation, as well as theory of "germplasm" A. Weismann, according to which acquired in the process of ontogeny, traits are not inherited.

Only the works of the Czech researcher G. Mendel (1822-1884) became the founding 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. Cermak, 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 deciphering of the fine structure of the gene and methods of regulation of gene activity, the search for genes that cause the development of hereditary human diseases and methods of their "correction", the creation of a new generation of drugs by type DNA vaccines, genetic and cellular engineering of organisms with new properties that could produce drugs and food products necessary for humans, as well as a complete decoding of the human genome.

Heredity and variability - properties of organisms

Heredity - This is the ability of organisms to transmit their traits and properties in a series of generations.

Variability - the property of organisms to acquire new characteristics during life.

Signs - any morphological, physiological, biochemical and other features of organisms, according to which some of them differ from others, for example, eye color. Propertiesany functional features of organisms are called, which are based on a certain structural feature or a group of elementary features.

The traits of organisms can be divided into quality and quantitative. Qualitative signs have two or three contrasting manifestations, which are called alternative signs, for example, blue and brown eye color, while quantitative (milk yield of cows, yield of wheat) do not have clear differences.

The material carrier of heredity is DNA. In eukaryotes, two types of inheritance are distinguished: genotypic and cytoplasmic. Carriers of genotypic heredity are localized in the nucleus and further we will talk about it, and the 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, however, their change can have a significant impact on the development of the body, 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 the productivity of the plant, and on the other, such variegated organisms are valued in decorative gardening. Such specimens are reproduced mainly asexually, since during sexual reproduction, ordinary green plants are more often obtained.

Genetic methods

The hybridological method, or the crossing method, consists in the selection of parental individuals and the analysis of the offspring. At the same time, the genotype of an organism is judged by the phenotypic manifestations of genes in the offspring obtained with a certain crossing pattern. This is the oldest informative method of genetics, which was most fully used 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 regions. They make it possible to identify genes of hereditary diseases even in embryos, establish paternity, etc.

The population-statistical method allows you to determine the genetic composition of the population, the frequency of certain genes and genotypes, the genetic load, as well as outline the prospects for the development of the population.

The method of hybridization of somatic cells in culture makes it possible to determine the localization of certain genes in chromosomes during the fusion of cells of various organisms, for example, a mouse and a hamster, a mouse and a human, etc.

Basic genetic concepts and symbols

Gene - This is a section of a DNA molecule, or chromosome, which carries information about a certain trait or property of an organism.

Some genes can influence the manifestation of several traits at once. This phenomenon is called pleiotropy. For example, a gene that causes the development of a hereditary disease of arachnodactyly (spider fingers) causes a curvature of the lens, 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), then in each of the paired chromosomes there is one copy of the gene responsible for a certain trait. Such genes are called allelic.

Allelic genes most often exist in two variants - dominant and recessive. Dominant is 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 indicated in capital letters Latin alphabet (A, B, C and etc.), and recessive ones - lowercase (a, b, from and etc.)- Recessive alleles can only appear if they occupy loci on both paired chromosomes.

An organism that has the same alleles in both homologous chromosomes is called homozygous for a given gene, or homozygote (AA , aa, AABB,aabb etc.), and an organism in which in both homologous chromosomes there are different variants of the gene - dominant and recessive - is called heterozygous for a given gene, or heterozygote (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. This phenomenon is called multiple allelism. However, even in this case, each chromosome from a pair carries only one allele, that is, all three variants of a gene 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 in many traits, it is possible to establish the patterns of their inheritance only by analyzing two or more traits in the offspring. Crossbreeding, in which inheritance is considered and an accurate quantitative registration of offspring is carried out for one pair of alternative characters, is called monohybrid, in two pairs - dihybrid, by more signs - polyhybrid.

By 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 a heterozygous one (Aa) will have a dominant allele in the phenotype. Therefore, to check the genotype of an organism with cross fertilization, they use analyzing cross - crossing, in which an organism with a dominant trait is crossed with a homozygous for a recessive gene. In this case, an organism homozygous for the dominant gene will not split in the offspring, while in the offspring of heterozygous individuals there is an equal number of individuals with dominant and recessive traits.

To record crossing schemes, the following conventions are most often used:

P (from lat. parent - parents) - parental organisms;

♀ (alchemical sign of Venus - a mirror with a handle) - a mother;

♂ (alchemical sign of Mars - shield and spear) - paternal individual;

x - sign of crossing;

F 1, F 2, F 3, etc. - hybrids of the first, second, third and subsequent generations;

F a - offspring from the analyzing cross.

Chromosomal theory of heredity

The founder of genetics G. Mendel, as well as his closest followers, did not have the slightest 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 allows explaining the splitting of hereditary factors according to Mendel, i.e., in their opinion, genes must be located on chromosomes. These assumptions became the cornerstone of the chromosomal theory of heredity.

In 1906, English geneticists W. Batson and R. Pennett discovered a violation of Mendelian splitting when crossing sweet peas, and their compatriot L. Doncaster discovered sex-linked inheritance in experiments with the goose moth butterfly. The results of these experiments clearly contradicted Mendelian ones, but considering that by that time it was already known that the number of known characters for experimental objects was much higher than 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, T. Morgan's group began experiments on a new experimental facility - the fruit fly Drosophila. The results of these experiments made it possible by the middle of the 20s of the XX century to formulate the main provisions of the chromosomal theory of heredity, to determine the order of arrangement of genes in chromosomes and the distance between them, that is, to draw up the first maps of chromosomes.

The main provisions of the chromosomal theory of heredity:

1) Genes are located on chromosomes. Genes of one chromosome are inherited jointly, 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 in chromosomes are arranged linearly.

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 understanding of the gene and genome

In the early 40s of the XX century, J. Beadle and E. Tatum, analyzing the results of genetic studies carried out on the neurospore mushroom, 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. Monod and A. Lvov succeeded in deciphering the structure of the E. coli gene and investigating the regulation of its activity. For this discovery, he was 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 sites include a promoter, operator, and terminator (Fig. 3.8). Promoter The name of the region of the gene to which the enzyme RNA polymerase is attached, which ensures the synthesis of mRNA during transcription. FROM operator, located between the promoter and the structural sequence, can bind repressor protein, does not allow RNA polymerase to start reading hereditary information from the coding sequence, and only its removal allows the start of transcription. The structure of the repressor is usually encoded in a regulatory gene located in another region of the chromosome. Reading information ends at a section of the gene called terminator.

Coding sequence a structural gene contains information about the amino acid sequence in the corresponding protein. The coding sequence in prokaryotes is called cistron, and the set 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 can also contain additional small circular or unclosed DNA molecules, which are called plasmids. Plasmids are able to integrate into chromosomes and be transmitted from one cell to another. They can carry information about sex 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 terminator. In addition, in the genes of eukaryotes, significant regions ( exons) alternate with insignificant ( introns), which are completely rewritten to mRNA and then cut out during their maturation. The biological role of introns is to reduce the likelihood of mutations at significant sites. The regulation of eukaryotic genes is much more complex than that described for prokaryotes.

The human genome. Each human cell contains about 2 m of DNA in 46 chromosomes, tightly packed in a double helix, which consists of about 3.2 x 10 9 nucleotide pairs, which provides about 10.19 billion possible unique combinations. By the end of the 80s of the XX century, the location of about 1,500 human genes was known, but their total number was estimated at about 100 thousand, since only hereditary diseases in humans are about 10 thousand, 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 XXI 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, about 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 repeating hundreds and thousands of times. Nevertheless, these genes encode a much larger number of proteins, for example tens of thousands of protective proteins - immunoglobulins.

97% of our genome is genetic "garbage" that exists only because it can reproduce well (RNAs that are transcribed in these regions never leave the nucleus). For example, among our genes there are not only "human" genes, but also 60% of genes similar to genes of the Drosophila fly, and up to 99% of genes have in common with chimpanzees.

In parallel with the decoding of the genome, mapping of chromosomes took place, as a result of which it was possible not only to discover, but also to determine the location of some genes responsible for the development of hereditary diseases, as well as target genes of drugs.

Deciphering the human genome has not yet given a direct effect, since we received a kind of instruction for assembling such a complex organism as a human, but did not learn how to make it or even correct errors in it. Nevertheless, the era of molecular medicine is already on the verge, the development of so-called gene drugs is underway all over the world 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 hereditary information of the cell and do not even encode a complete set of proteins necessary for their own functioning, they can significantly affect some of the characteristics of the organism. Thus, variegation in plants of chlorophytum, ivy and others is inherited by a small number of descendants, even when two variegated plants are crossed. This is due to the fact that plastids and mitochondria are transmitted for the most part with the cytoplasm of the egg, so this inheritance is called maternal, or cytoplasmic, in contrast to genotypic, which is localized in the nucleus.

3.5. Regularities of heredity, their cytological foundations. Mono- and dihybrid crossing. The patterns of inheritance established by G. Mendel. Linked inheritance of traits, gene linkage disorder. T. Morgan's laws. Chromosomal theory of heredity. Genetics of sex. Inheritance of sex-linked traits. Genotype as an integral system. Development of knowledge about the genotype. The human genome. Interaction of genes. Solving genetic problems. Drawing up crossing schemes. G. Mendel's laws and their cytological foundations.

Regularities 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 lines - chromosomes, then schematically homozygous individuals can be written as A || A or a || a, while heterozygous - A || a. When gametes are formed during meiosis, each of the genes of a heterozygote pair will be in one of the sex cells (Fig. 3.9).

For example, if you cross two heterozygous individuals, then provided that only a pair of gametes is formed in each of them, it is possible to obtain only four daughter organisms, three of which will carry at least one dominant gene AND, and only one will be homozygous for the recessive gene and, that is, the patterns of heredity are statistical in nature (Fig. 3.10).

In cases where genes are located in different chromosomes, then during the formation of gametes, the distribution of alleles from a given pair of homologous chromosomes between them 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 a variety of allele recombinations 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 in the offspring it is possible to fix an independent splitting for each pair of characters (Fig. 3.11).

However, the number of signs 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 gametes are formed in some individual heterozygous for two pairs of genes located in homologous chromosomes, then one should take into account not only the probability of the 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 appear in the offspring. The data obtained in experiments on Drosophila formed the basis chromosomal 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 caused by the loss of a small section of one of the chromosomes.

Regularities of inheritance, established by G. Mendel, their cytological basis (mono- and dihybrid crossing)

The main regularities of the independent inheritance of traits were discovered by G. Mendel, who achieved success by applying in his studies a new hybridological method at that time.

G. Mendel's success was due to the following factors:

1.a good choice of the object of research (sowing pea), which has a short growing season, is a self-pollinated plant, gives a significant amount of seeds and is represented by a large number of varieties with well-distinguishable characteristics;

2. using only pure lines of peas, 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. precise quantitative calculation of the offspring obtained.

For research G. Mendel selected only seven signs with alternative (contrasting) manifestations. Already in the first crosses, he noticed that in the offspring of the first generation, when crossing plants with yellow and green seeds, 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 were named by G. Mendel dominant. The same ones that did not appear in the first generation were named recessive.

Individuals that gave splitting in the offspring were named heterozygous, and individuals that did not split, - homozygous.

Table 3.1

Pea traits, the inheritance of which was studied by G. Mendel

Crossing in which the manifestation of only one trait is investigated 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 "color of the flower corolla" in peas has only two manifestations - red and white. All other signs characteristic of these organisms are not taken into account and are not taken into account in the calculations.

The monohybrid crossing scheme is as follows:

By 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 on other grounds, which gave G. Mendel reason to formulate the law of uniformity of the first generation hybrids, which is also called Mendel's first law and the law of domination.

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.

When self-pollinating (crossing) hybrids of the first generation, it turned out that 6022 seeds are yellow, and 2001 - green, which approximately corresponds to a ratio of 3: 1. The discovered pattern was named the law of splitting, or Mendel's second law.

Mendel's second law:

When crossing heterozygous hybrids of the first generation in the offspring, there will be a predominance of one of the traits in a ratio of 3: 1 by phenotype (1: 2: 1 by genotype).

However, according to the phenotype of an individual, it is far from always possible to establish its genotype, since as homozygotes for the dominant gene (AA), and heterozygotes (Aa) will have a dominant gene manifestation in the phenotype. Therefore, for organisms with cross fertilization, analyzing cross - crossing, in which an organism with an unknown genotype is crossed with a homozygote for a recessive gene to check the genotype. At the same time, homozygous individuals for the dominant gene do not split in the offspring, while in the offspring of heterozygous individuals there is an equal number of individuals with both dominant and recessive traits:

Based on the results of his own experiments, G. Mendel suggested that hereditary factors during the formation of hybrids do not mix, but remain unchanged. Since the connection between generations is carried out through gametes, he admitted that in the process of their formation, only one factor from a pair gets into each of the gametes (that is, the gametes are genetically pure), and during fertilization the pair is restored. These assumptions are called rules of gamete purity.

Gamete purity rule:

During gametogenesis, the genes of one pair are separated, that is, each gamete carries only one variant of the gene.

However, organisms differ from each other in many ways, therefore, it is possible to establish the patterns of their inheritance only by analyzing two or more characters in the offspring. Crossbreeding, in which inheritance is considered and an accurate quantitative accounting 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 crossing.

Dihybrid crossing scheme:

With a greater variety of gametes, the determination of the genotypes of offspring becomes difficult, therefore, for analysis, the Pennett lattice is widely used, into which male gametes are entered horizontally, and female gametes are entered vertically. The genotypes of the offspring are determined by the combination of genes in columns and rows.

For dihybrid crossing, G. Mendel chose two characters: 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 seeds. The calculation showed that the cleavage was close to 9: 3: 3: 1, but for each of the signs the ratio of 3: 1 was maintained (yellow - green, smooth - wrinkled). This pattern was named the law of independent splitting of features, 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, an independent splitting of these traits will occur in a ratio of 3: 1 (9: 3: 3: 1 with a dihybrid crossing).

Mendel's third law applies only to cases of independent inheritance, when genes are located in different pairs of homologous chromosomes. In cases where genes are located in one pair of homologous chromosomes, the laws of linked inheritance are valid. The patterns of independent inheritance of traits established by G. Mendel are also often violated in the interaction of genes.

T. Morgan's laws: linked inheritance of traits, disruption 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 are much larger than the chromosomes. In accordance with the chromosomal theory of heredity, genes located on the same chromosome are inherited linked. As a consequence, in dihybrid crossing, 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 in the second generation, it gives the initial phenotypes in a ratio of 3: 1, and when analyzing crossing of hybrids of the first generation, the cleavage 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. A gray body and long wings are dominant features. 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, mainly parental phenotypes were actually obtained in a ratio close to 3: 1, but there was also a small number of individuals with new combinations of these traits ( (See Figure 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 cleavage with crossing over, which occurs in prophase I of meiosis, and suggested that the unit of distance between genes in the chromosome is 1% crossing over, which was later named Morganida in his honor.

The patterns of linked inheritance, established during experiments on Drosophila, are called T. Morgan's law.

Morgan's Law:

Genes localized on one chromosome occupy a certain place, called a locus, and are inherited linked, and the strength of the link is inversely proportional to the distance between 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 linking is disrupted during crossing over as a result of the exchange of regions of homologous chromosomes.

The phenomena of gene linkage and crossing over make it possible to construct maps of chromosomes with the order of genes placed on them. Genetic chromosome maps have been created for many genetically well-studied objects: Drosophila, mice, humans, corn, wheat, peas, etc. The study of genetic maps allows comparing the structure of the genome in different types of organisms, which is important for genetics and breeding, as well as evolutionary research ...

Genetics of gender

Floor - This is a set of morphological and physiological characteristics of an organism 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 another are divided into primary and secondary. The primary sexual characteristics are the genitals, and all the rest are secondary.

In humans, secondary sexual characteristics are body type, tone of voice, predominance of muscle or adipose tissue, the presence of hair on the face, 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, the voice is high. Men differ from them in wider shoulders, a 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. The explanation for this was obtained by studying the karyotypes of insects. It turned out that 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 in advance the sex of the offspring. However, later it was 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 the chromosomes in pairs.

A similar difference was also found in the human karyotype: males have two unpaired chromosomes. In shape, these chromosomes at the beginning of division resemble the Latin letters X and Y, and therefore were named X and Y chromosomes. A man's sperm can carry one of these chromosomes and determine the sex of the unborn child. In this regard, the chromosomes of humans and many other organisms are divided into two groups: autosomes and heterochromosomes, or sex chromosomes.

TO autosomes include chromosomes that are the same for both sexes, while sex chromosomes - These are chromosomes that differ in different sexes and carry information about sex characteristics. In cases where the sex carries the same sex chromosomes, for example XX, it is said that he homozygous or homogametic (forms the same gametes). The other sex, which has different sex chromosomes (XY), is called hemizygous (not having a full allelic equivalent), or heterogametic. In humans, most mammals, the Drosophila fly and other organisms, the female sex is homogametic (XX), and the male is heterogametic (XY), while in birds the male sex 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 severe hereditary diseases in humans, such as hemophilia and color blindness. The Y chromosome, on the other hand, is very small, it contains only about a dozen genes, including specific genes responsible for male development.

The karyotype of a man is written as ♂46, XY, and the karyotype of a woman 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 one.

Bees differ from other organisms in that females develop from fertilized eggs, and males from unfertilized ones. Their sex ratio differs from that indicated above, since the fertilization process is regulated by the uterus, in the genital tract of which spermatozoa are stored for the whole year since spring.

In a number of organisms, sex can be determined in a different way: before fertilization or after it, depending on the environmental conditions.

Inheritance of sex-linked traits

Since some genes are found on sex chromosomes that are not the same in representatives of opposite sexes, the nature of inheritance of the traits encoded by these genes differs from the general one. This type of inheritance is called kris-cross inheritance, since men inherit the characteristics of the mother, and women inherit the father. Traits determined by genes that are located on the sex chromosomes are called bonded to the floor. Examples of sex-linked traits are recessive traits of hemophilia and color blindness, which are mainly manifested in males, since 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 a mother was a heterozygous carrier of hemophilia, then half of her sons will have impaired blood clotting: X n - normal blood clotting X h - incoagulability of blood (hemophilia)

Traits encoded in the genes of the Y chromosome are transmitted exclusively through the male line and are called Dutch (the presence of a membrane between the toes, increased hairiness of the edge of the auricle).

Gene interaction

Checking 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, hybrids of the first generation have corollas painted pink, while in the second generation there are individuals with red, pink and white flowers in a ratio of 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 traits of other genes or suppress them. These observations became the basis for the concept of the genotype as a system of interacting genes. At present, 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 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 the dominant one, as in the case of the color of the corolla of a night beauty (white + red \u003d pink) and wool in cattle.

Codominating call this type of interaction of allelic genes in which both alleles are manifested 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 group in humans (genotype - I A I B).

As can be seen from the table, blood groups I, II and III are inherited according to the type of complete dominance, while group IV (AB) (genotype - I A I B) is a case of codominance.

Overdominance - this is a phenomenon in which in a heterozygous state the dominant trait manifests itself much more strongly than in a homozygous one; overdominance is often used in breeding and is considered 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 a homozygous state, lead to the death of the organism most often in the embryonic period. The reason for the death of offspring is the pleiotropic effect of genes for gray coat color in astrakhan sheep, platinum color in foxes, and lack of scales in mirror carps. When two individuals heterozygous for these genes are crossed, the splitting according to the studied trait in the offspring will be equal to 2: 1 due to the death of 1/4 of the offspring.

The main types of interaction between non-allelic genes are complementarity, epistasis, and polymeria. 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 interaction of non-allelic genes in which one non-allelic gene suppresses the development of another trait. For example, in chickens, plumage color is determined by one dominant gene, while another dominant gene suppresses color development, as a result of which most chickens have white plumage.

Polymer is called a phenomenon in which non-allelic genes have the same effect on the development of a trait. In this way, quantitative characteristics are most often coded. For example, human skin color is determined by at least four pairs of non-allelic genes - the more dominant alleles in a genotype, the darker the skin.

Genotype as 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 the environmental conditions, although if a part of the body with white hair is shaved off in an ermine rabbit and an ice pack is applied to it, then over time, black wool will grow in this place.

The development of quantitative traits is much more dependent on environmental conditions. For example, if modern wheat varieties 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; however, they are manifested only in interaction with environmental conditions.

In addition, genes interact with each other and, once 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 awn of the seed 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 not excluded that each gene is simultaneously a gene of the main action for "its" trait and a modifier for other traits. Thus, the phenotype is the result of the interaction of genes of the entire genotype with the environment in the ontogeny of an 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 in which the interaction of genes gave the most favorable reaction in ontogenesis survived.

Human genetics

For man as a biological species, the genetic laws 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 branches of genetics.

Human genetics is both a fundamental and an applied science, since it is engaged in the study of hereditary human diseases, of which more than 4 thousand have already been described. It stimulates the development of modern trends in general and molecular genetics, molecular biology and clinical medicine. Depending on the problematics, human genetics is divided into several directions, frolicking into independent sciences: genetics of normal human traits, medical genetics, genetics of behavior and intelligence, 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, the small number of offspring, the impossibility of directed crosses for genetic analysis, the lack of pure lines, insufficient accuracy of registration of hereditary traits and small pedigrees, the impossibility of creating identical and strictly controlled conditions for the development of offspring from different marriages, relatively a large number poorly distinguished chromosomes and the impossibility of experimental obtaining mutations.

Methods for studying human genetics

The methods used in human genetics do not fundamentally differ from those generally accepted for other objects - these are genealogical, twin, cytogenetic, dermatoglyphic, molecular biological and population statistical methods, somatic cell hybridization methodand 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 sick at the same time.

Dermatoglyphic method based on the study of the individual characteristics of the skin patterns of the fingers (fingerprinting), palms and feet. Based on these features, it often allows timely identification of hereditary diseases, in particular chromosomal abnormalities, such as Down syndrome, Shereshevsky-Turner syndrome, etc.

Genealogical method - this is a method of compiling genealogies, with the help of which they determine the nature of inheritance of the studied traits, including hereditary diseases, and predict the birth of offspring with the corresponding traits. It made it possible to reveal the hereditary nature of such diseases as hemophilia, color blindness, Huntington's chorea, etc. even before the discovery of the basic laws of heredity. When drawing up pedigrees, they keep records of each of the family members and take into account the degree of kinship 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 a person whose pedigree is compiled - proband, - on the paternal and maternal lines, otherwise they collect information about several families in which this feature is manifested. The genealogical method makes it possible 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 monarchs of the Habsburgs, the inheritance of prognathia (strongly protruding lower lip) and "royal hemophilia" among the descendants of the British Queen Victoria (Fig. 3.14).

Solving genetic problems. Drawing up crossing schemes

The whole variety of genetic problems can be reduced to three types:

1. Computational tasks.

2. Tasks for determining the genotype.

3. Tasks to establish the type of inheritance of a trait.

Feature calculation tasks 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.

TOPIC 2. SOCIO-BIOLOGICAL BASES OF PHYSICAL CULTURE

Introduction

1. Organism as a biological system.

2. Anatomical - morphological features of the organism.

3. The skeletal system and its functions.

4. 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 between physical and mental activity.

8. Means of physical culture, providing resistance to mental and physical performance.

9.Functional indicators of the body's fitness at rest and when performing extremely strenuous work.

10. Exchange of substances and energy.

11. Control questions.

Introduction

Socio-biological foundations of physical culture are the principles of interaction of social and biological laws in the process of mastering the values \u200b\u200bof physical culture by a person.

Man obeys biological laws inherent in all living things. 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 of life and social relationships. Labor and the influence of the social environment in the process of human development have influenced the biological characteristics of the body of a modern person and his environment. The organism is a well-coordinated single self-regulating and self-developing biological system, the functional activity of which is due to 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 human health, their performance, life expectancy and fertility (reproductive capacity). Without knowledge about the structure of the human body, about the regularities of the functioning of individual organs and systems of the body, about the peculiarities of the complex processes of its vital activity, it is impossible to organize the process of forming a healthy lifestyle and physical training of the population, including students. The achievements of biomedical sciences underlie the pedagogical principles and methods of the educational and training process, the theory and methods 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, which largely determine individual development in the process of his later life. Once after birth in an autonomous regime, the child grows rapidly, increasing the mass, length and surface area of \u200b\u200bhis body. Human growth continues until about 20 years of age. Moreover, in girls, the highest growth rate is observed in the period from 10 to 13, and in boys from 12 to 16 years. The increase in body weight occurs almost in parallel with the increase in its length and stabilizes by 20-25 years.

It should be noted that over the past 100-150 years in a number of countries there has been an early morphological and functional development of the body in children and adolescents. This phenomenon is called acceleration (Latin accelera-tio-acceleration).

Elderly age (61-74 years) and senile (75 years and more) are characterized by physiological processes of restructuring: a decrease in the active capabilities of the organism and its systems - immune, nervous, circulatory, etc. A healthy lifestyle, active motor activity during life significantly slows down the process aging.

The vital activity of the organism is based on the process of automatically maintaining vital factors at the required level, any deviation from which leads to the immediate mobilization of mechanisms that restore this level.

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