Organism as a biological system: features, functions and brief theory

method of reproduction

peculiarities

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 cell. The bud grows, reaches the size of the mother, and separates

Single-celled eukaryotes, some ciliates, yeast

sporulation

A spore is a special cell, covered with a dense shell that protects from external influences

Spore plants; some protozoa

vegetative propagation:

An increase in the number of individuals of a given species occurs by separating the viable parts of the vegetative body of the organism

Plants, animals

In plants

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

Lily, nightshade, gooseberry, etc.

In animals

Ordered and unordered division

Coelenterates, starfish, annelids

peculiarities

prezygotic

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

embryonic period

zygote (unicellular stage of development of a multicellular organism)

contains yolk grains, mitochondria, pigments, the cytoplasm moves, pronounced bilateral symmetry (bilateral). In a number of animal species, protein and new RNA synthesis begins

splitting up

cleavage furrows 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 fragmentations, a group of cells closely adjacent to each other is formed. The embryo resembles a raspberry. It was called morula.

blastulation

the final stage of egg crushing. In the lancelet, the blastula is formed when the embryo reaches 128 cells. The blastula has the shape of a vesicle 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 embryo body (germ layers): ectoderm, endoderm and mesoderm. The development of sponges and coelenterates ends at the stage of two germ layers. All other organisms higher on the evolutionary ladder develop three germ layers.

histogenesis and organogenesis

formation of tissues and organs occurs

reasons for the manifestation

meaning

Non-hereditary (modification variability)

change in environmental conditions, as a result of which the organism changes within the limits of the reaction norm specified by the genotype

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

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

Hereditary (genotypic)

Mutational

the influence of external and internal mutagenic factors, resulting in changes in genes and chromosomes

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

reproductive isolation > new species, genera > microevolution.

Combinative

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

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.

Correlative (correlative)

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

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

long-legged animals have long necks.

aromorphosis

idioadaptation

general degeneration

hypergenesis

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

Galapagos finches ( Various types beaks)

In bivalves, the disappearance of the head

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

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

The pork tapeworm has a “loss” of the digestive system.

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

Ladybugs and salamanders have warning coloration

Loss of vision in moles, proteas, 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. External environment and its impact on the body and human life 6

3. Means physical culture, providing stability to mental and physical performance 8

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

Conclusion 16

References 19

Introduction

Medical, biological and pedagogical sciences deal with man as a being not only biological, but also social. Sociality is the specific essence of a person, which does not abolish his biological substance, because the biological origin of a person is a necessary condition for the formation and manifestation of a social way of life. Meanwhile, it is not organisms who create history, change the living and inanimate world, create and destroy, set world and Olympic records, but people, human individuals. Thus, the socio-biological foundations of physical culture are the principles of interaction of social and biological laws in the process of a person mastering the values ​​of physical culture.

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 beings. However, it differs from representatives of the animal world not only in structure, but also in developed thinking, intelligence, speech, and the characteristics of social and living conditions and social relationships. Labor and the influence of the social environment in the process of human development have influenced the biological characteristics of the modern human body and its 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 organism is a coherent united self-regulating and self-developing biological system, the functional activity of which is determined by the interaction of mental, motor and autonomic reactions to environmental influences, which can be both beneficial and detrimental to health. Distinctive feature human – conscious and active influence on external natural and social conditions that determine the state of people’s health, their performance, life expectancy and fertility (reproduction).

Without knowledge about the structure of the human body, about the patterns of functioning of individual organs and systems of the body, about the peculiarities of the complex processes of its life, it is impossible to organize the process of forming a healthy lifestyle and physical training of the population, including students. Achievements of medical and biological sciences underlie the pedagogical principles and methods of the educational and training process, the theory and methodology 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 body occurs during all periods of its life - from the moment of conception to death. This development is called individual, or development in ontogenesis. In this case, two periods are distinguished: intrauterine (from the moment of conception to 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 course of his future life.

Finding himself after birth, figuratively speaking, in autonomous conditions, the child grows rapidly, the mass, length and surface area of ​​his body increases. Human growth continues until approximately 20 years of age. Moreover, in girls the greatest intensity of growth is observed in the period from 10 to 13, and in boys from 12 to 16 years. An increase in body weight occurs almost in parallel with an increase in its length and stabilizes by 20–25 years.

It should be noted that over the past 100–150 years, early morphofunctional development of the body in children and adolescents has been observed in a number of countries. This phenomenon is called acceleration (Latin acce1era - acceleration), it is associated not only with the acceleration of growth and development of the body in general, but also with the earlier onset of puberty, the accelerated development of sensory (Latin boar - feeling), motor coordination and mental functions . Therefore, the boundaries between age periods are quite 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) is associated with a period of maturation, when all organs, their systems and apparatuses reach their morphofunctional maturity. Mature age (22 – 60 years) is characterized by minor changes in body structure, and the functionality of this fairly long period of life is largely determined by the characteristics of lifestyle, nutrition, and physical activity. Old 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 body and its systems - immune, nervous, circulatory, etc. A healthy lifestyle, active motor activity during life significantly slow down the aging process .

The vital activity of the body 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 ensure the maintenance or restoration of the relatively dynamic constancy of the internal environment and certain physiological functions of the human body (blood circulation, metabolism, thermoregulation, etc.). This process is ensured 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 make it possible to maintain the constancy of the composition, physicochemical and biological properties of the internal environment, despite changes in the external world and physiological changes that arise during the life of the body. In the 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, as they are washed by blood, lymph and tissue fluid. The constancy of the physical and chemical 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. Violation 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 unique functions in the overall structural and functional system of the body, are supplied with nutrients and the necessary amount of oxygen in order to carry out the vital processes of energy generation, removal of decay products, ensuring various biochemical reactions of life, etc. .d. These processes occur thanks to regulatory mechanisms that operate through the nervous, circulatory, respiratory, endocrine and other systems of the body.

2. External environment and its impact on the human body and life activity

External environment . A person is influenced by various environmental factors. When studying the diverse types of its activities, one cannot 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 everyday, economic, industrial and creative human activity.

From the external environment, the body receives substances necessary for its life and development, as well as irritants (useful and harmful) that disrupt the constancy of the internal environment. The body, through the interaction of functional systems, strives in every possible way 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 quite rigid (for example, blood pH 7.36 - 7.40, body temperature - within 35 - 42" 0), others and are normally characterized by significant fluctuations (for example, 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, find themselves in power of environmental factors. For example, a frog, not having a mechanism that regulates the constancy of body temperature, duplicates the temperature of the external environment so much that in winter all its life processes are inhibited, and in the summer, being far from water, it dries out and dies. In the process of phylogenetic development higher animals, including humans, seemed to place themselves in a greenhouse, creating their own stable internal environment and thereby ensuring 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, teaching) is both a field of knowledge, and a part of biology, and an academic discipline, and complex science. Ecology examines the relationships of organisms with each other and with the inanimate components of nature: the Earth (its biosphere). Human ecology studies the patterns of human interaction with nature, the problems of preserving and promoting health. Man depends on the conditions of his environment in the same way as 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 technological violations) threatens the existence of man himself. For example, in large cities the natural habitat is significantly deteriorating, the rhythm of life, the psycho-emotional situation of work, life, and recreation are being disrupted, and 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, and air pollution is lower. All these changes have an extremely adverse effect on physical and mental health of a person. About 80M diseases of modern man are the result of deterioration ecological situation on the planet. Environmental problems are directly related to the process of organizing and conducting systematic physical exercise and sports, as well as to the conditions in which they occur.

3.2. Reproduction of organisms, its significance. Methods of reproduction, similarities and differences between sexual and asexual reproduction. The use of sexual and asexual reproduction in human practice. The role of meiosis and fertilization in ensuring the constancy of the number of chromosomes over generations. Application of artificial insemination in plants and animals.

3.3. Ontogenesis and its inherent patterns. Specialization of cells, formation of tissues and organs. Embryonic and postembryonic development of organisms. Life cycles and alternation of generations. Causes of disturbances in the development of organisms.

3.5. Patterns of heredity, their cytological basis. Mono- and dihybrid crossing. Patterns of inheritance established by G. Mendel. Linked inheritance of traits, disruption of gene linkage. 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. Human genome. Gene interaction. Solving genetic problems. Drawing up crossing schemes. G. Mendel's laws and their cytological foundations.

3.6. Variability of characteristics in organisms: modification, mutation, combination. Types of mutations and their causes. The meaning of variability in the life of organisms and in evolution. Norm of reaction.

3.6.1. Variability, its types and biological significance.

3.7. The harmful effects of mutagens, alcohol, drugs, nicotine on the genetic apparatus of the cell. Protection of the environment from 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. Selection, its objectives and practical significance. Teachings of N.I. Vavilov about the centers of diversity and origin of cultivated plants. The law of homological series in hereditary variability. Methods for breeding new plant varieties, animal breeds, and strains of microorganisms. The importance of genetics for selection. Biological principles of growing cultivated plants and domestic animals.

3.8.1. Genetics and selection.

3.8.2. Working methods of I.V. Michurina.

3.8.3. Centers of origin of cultivated plants.

3.9. Biotechnology, cellular 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, and preservation of the planet’s gene pool. Ethical aspects of the development of some research in biotechnology (human cloning, targeted changes in the genome).

3.9.1. Cellular and genetic engineering. Biotechnology.

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

Unicellular and multicellular organisms

The extraordinary diversity of living beings on the planet forces us to find different criteria for their classification. Thus, they are classified as cellular and non-cellular forms of life, since cells are the structural unit of almost all known organisms - plants, animals, fungi and bacteria, while viruses are non-cellular forms.

Depending on the number of cells that make up the organism and the degree of their interaction, unicellular, colonial and multicellular organisms are distinguished. Despite the fact that all cells are morphologically similar and are capable of performing normal cell functions (metabolism, maintaining homeostasis, development, etc.), the cells of unicellular organisms perform the functions of an entire organism. Cell division in unicellular organisms entails an increase in the number of individuals, and in their life cycle there are no multicellular stages. In general, unicellular organisms have the same cellular and organismal levels of organization. The vast majority of bacteria, some animals (protozoa), plants (some algae) and fungi are unicellular. Some taxonomists even propose to separate unicellular organisms into a special kingdom - protists.

Colonial are organisms in which, during the process of asexual reproduction, daughter individuals remain connected to the maternal organism, forming a more or less complex association - a colony. In addition to colonies of multicellular organisms, such as coral polyps, there are also colonies of unicellular organisms, in particular pandorina and eudorina algae. Colonial organisms apparently were an intermediate link in the process of the emergence of multicellular organisms.

Multicellular organisms, without a doubt, have a higher level of organization than unicellular organisms, since their body is formed by many cells. Unlike colonial organisms, which can also have more than one cell, in multicellular organisms the cells are specialized to perform various functions, which is reflected in their structure. The price for this specialization is the loss of the ability of their cells to exist independently, and often to reproduce their own kind. The division of a single cell leads to the growth of a multicellular organism, but not to its reproduction. Ontogenesis of multicellular organisms is characterized by the process of fragmentation of a fertilized egg into many blastomere cells, from which an organism with differentiated tissues and organs is subsequently formed. Multicellular organisms are usually larger than unicellular ones. An increase in body size in relation to their surface contributed to the complexity and improvement of metabolic processes, the formation of the internal environment and, ultimately, provided them with greater resistance to environmental influences (homeostasis). Thus, multicellular organisms have a number of advantages in organization compared to unicellular organisms and represent a qualitative leap in the process of evolution. Few bacteria, most plants, animals and fungi are multicellular.

Autotrophs and heterotrophs

According to the method of nutrition, all organisms are divided into autotrophs and heterotrophs. Autotrophs are able to independently synthesize organic substances from inorganic ones, while heterotrophs use exclusively ready-made organic substances.

Some autotrophs can use light energy to synthesize organic compounds - such organisms are called photoautotrophs; they are capable of photosynthesis. Plants and some bacteria are photo-autotrophs. Closely related to them are 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 into 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

Characteristics of viruses

Along with the cellular form of life, there are also non-cellular forms of life - viruses, viroids and prions. Viruses (from the Latin vira - poison) are the smallest living objects that are incapable of displaying any signs of life outside cells. The fact of their existence was proven back in 1892 by the Russian scientist D.I. Ivanovsky, who established that a 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 "Herrel isolated the first virus - a bacteriophage. Viruses are studied by the science of virology (from the Latin vira - poison and the Greek logos - word, science).

Nowadays, about 1000 viruses are already known, which are classified according to the objects they damage, shape and other characteristics, but the most common is the classification 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 shell - a capsid. The capsid is not monolithic; it is assembled from protein subunits - capsomeres. In complex viruses, the capsid is covered with a lipoprotein membrane - a supercapsid, which also includes glycoproteins and non-structural enzyme proteins. Bacterial viruses have the most complex structure - bacteriophages (from the Greek bacterion - rod and phagos - eater), which have a head and a process, or “tail”. The head of the bacteriophage is formed by a protein capsid and a nucleic acid enclosed in it. In the tail there is a protein sheath and a hollow rod hidden inside it. At the bottom of the rod there is a special plate with spikes and threads responsible for the interaction of the bacteriophage with the cell surface.

Unlike cellular life forms, which have both DNA and RNA, viruses contain only one type of nucleic acid (either DNA or RNA), so they are divided into DNA smallpox viruses, herpes simplex viruses, 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 a single-stranded molecule, and RNA can be a double-stranded molecule.

Since viruses lack organelles of movement, infection occurs through direct contact of the virus with the cell. This mainly occurs through the air (influenza), through the digestive system (hepatitis), blood (HIV) or through a vector (encephalitis virus).

Viruses can enter the cell directly by accident, with 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 ends up in the cytoplasm. Most viruses do not penetrate into any cell of the host body, but into a strictly defined one, for example, hepatitis viruses infect liver cells, and influenza viruses infect cells of the mucous membrane of the upper respiratory tract, since they are able to interact with specific receptor proteins on the surface of the cell membrane - host, which are absent in other cells.

Due to the fact that the cells of plants, bacteria and fungi have strong cell walls, the viruses that infect these organisms have developed appropriate adaptations for penetration. Thus, bacteriophages, after interacting with the surface of the host cell, “pierce” it with their rod and introduce nucleic acid into the cytoplasm of the host cell (Fig. 3.2). In fungi, infection occurs mainly when cell walls are damaged; in plants, both the above-mentioned route and the penetration of the virus through plasmodesmata are possible.

After penetration into the cell, the virus “undresses,” that is, the capsid is lost. Further events depend on the nature of the nucleic acid of the virus: DNA-containing viruses integrate their DNA into the genome of the host cell (bacteriophages), and DNA is either first synthesized on RNA, which is then integrated into the genome of the host cell (HIV), or it can directly protein synthesis occurs (influenza virus). Reproduction of the viral nucleic acid and synthesis of capsid proteins using the protein synthesizing apparatus of the cell are essential components of a viral infection, after which self-assembly of viral particles occurs and their exit from the cell. Viral particles in some cases leave the cell, gradually budding from it, and in other cases a microexplosion occurs, accompanied by cell death.

Viruses not only inhibit the synthesis of their own macromolecules in the cell, but are also capable of causing damage to cellular structures, especially during a mass exit from the cell. This leads, for example, to the mass death of industrial cultures of lactic acid bacteria in the event of damage by certain bacteriophages, impaired immunity due to the destruction of HIV T4 lymphocytes, which are one of the central links of the body’s defenses, to numerous hemorrhages and death of a person as a result of infection with the Ebola virus, to cell degeneration and the formation of a cancerous tumor, etc.

Despite the fact that viruses that have entered a cell often quickly suppress its repair systems and cause death, another scenario is also likely - activation of the body's defenses, which is associated with the synthesis of antiviral proteins, such as interferon and immunoglobulins. In this case, the reproduction of the virus is interrupted, new viral particles are not formed, and the remnants of the virus are removed from the cell.

Viruses cause numerous diseases in humans, animals and plants. In plants this is a mosaic of tobacco and tulips, in humans - influenza, rubella, measles, AIDS, etc. In the history of mankind, the viruses of black pox, the Spanish flu, and now HIV have claimed the lives of hundreds of millions of people. However, infection can also increase the body’s resistance to various pathogens (immunity), and thus contribute to their evolutionary progress. In addition, viruses are able to “grab” parts of the host cell’s genetic information and transfer them to the next victim, thereby 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 of implementation of hereditary information; they are used as a tool for genetic engineering and biological control of pathogens of certain diseases of plants, fungi, animals and humans.

AIDS and HIV infection

HIV (human immunodeficiency virus) was discovered only in the early 80s of the 20th century, but the speed of spread of the disease it causes and the impossibility of a cure at this stage of medical development force us to pay increased attention to it. In 2008, F. Barré-Sinoussi and L. Montagnier were awarded the Nobel Prize in Physiology or Medicine for their research on HIV.

HIV is a complex RNA virus that primarily affects T4 lymphocytes, which coordinate the work of the entire immune system (Fig. 3.3). Using the RNA of the virus, DNA is synthesized using the enzyme RNA-dependent DNA polymerase (reverse transcriptase), which is integrated into the genome of the host cell, converted into a provirus and “hidden” for an indefinite time. Subsequently, from this section of DNA, information about the viral RNA and proteins begins to be read, which are collected into viral particles and almost simultaneously leave it, dooming it to death. Viral particles infect more and more new cells and lead to a decrease in immunity.

HIV infection has several stages, and for a long period a person can be a carrier of the disease and infect other people, but no matter how long this period lasts, the last stage still occurs, which is called acquired immunodeficiency syndrome, or AIDS.

The disease is characterized by a decrease and then a complete loss of the body’s immunity to all pathogens. Signs of AIDS are chronic damage to the mucous membranes of the oral cavity and skin by pathogens of viral and fungal diseases (herpes, yeast, etc.), severe pneumonia and other AIDS-associated diseases.

HIV is transmitted sexually, through blood and other body fluids, but is not transmitted through handshakes or household objects. At first, in our country, HIV infection was more often associated with promiscuity, especially homosexual sex, injection drug addiction, and contaminated blood transfusions; currently, the epidemic has spread beyond risk groups and is quickly spreading to other categories of the population.

The main means of preventing the spread of HIV infection are the use of condoms, choosiness in sexual relations and abstinence from drug use.

Measures to prevent the spread of viral diseases

The main means of preventing viral diseases in humans is wearing gauze bandages when in contact with sick people. respiratory tract, washing hands, vegetables and fruits, disinfecting habitats of carriers of viral diseases, vaccination against tick-borne encephalitis, sterilization of medical instruments in medical institutions etc. To avoid HIV infection, you should also abstain from drinking alcohol, drugs, have a single sexual partner, use personal protective equipment during sexual intercourse, etc.

Viroids

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

Their nucleic acid probably does not encode their own proteins, but is only reproduced in the cells of the host plant using its enzyme systems. Often it can also cut the DNA of the host cell into several parts, thereby dooming the cell and the plant as a whole to death. Thus, several years ago, viroids caused the death of millions of coconut trees in the Philippines.

Prions

Prions (abbr. proteinaceous infectious and -on) are small infectious agents of a protein nature, in the form of a thread 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 dysfunction of tissues and organs, especially the central nervous system, and the development of currently incurable diseases: “mad cow disease”, Creutzfeldt-Jakob disease, kuru, etc.

3.2. Reproduction of organisms, its significance. Methods of reproduction, similarities and differences between sexual and asexual reproduction. The use of sexual and asexual reproduction in human practice. The role of meiosis and fertilization in ensuring the constancy of the number of chromosomes over generations. Application 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 life. Despite the fact that life as a whole is continuous, the lifespan of an individual individual is finite, therefore the transfer of hereditary information from one generation to the next during reproduction ensures the survival of a given type of organism over long periods of time. Thus, reproduction ensures continuity and continuity of life.

A prerequisite for reproduction is to obtain more offspring than parent individuals, since not all descendants will be able to survive to the stage of development at which they themselves will be able to produce offspring, since they can be destroyed by predators, die from diseases and natural disasters, such as fires, floods, etc.

Methods of reproduction, similarities and differences between sexual and asexual reproduction

In nature, there are two main methods of reproduction - asexual and sexual.

Asexual reproduction is a method of reproduction in which neither the formation nor fusion of specialized sex cells - gametes - occurs; only one parent organism takes part in it. Asexual reproduction is based on mitotic cell division.

Depending on how many cells of the mother’s body give rise to a new individual, asexual reproduction is divided into asexual and vegetative. In actual asexual reproduction, the daughter individual develops from a single cell of the mother's body, and in vegetative reproduction, from a group of cells or an entire organ.

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

Binary fission is essentially a simple mitotic division of a single-celled mother organism, in which the nucleus divides first, and then the cytoplasm. It is characteristic of various representatives of the plant and animal kingdom, for example, the amoeba proteus and the ciliate slipper.

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

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

A typical example of budding as a type of asexual reproduction proper is the budding of yeast, 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. In this way, the ability of the mother cell to further divide is preserved, and the number of individuals quickly increases.

Vegetative reproduction can be carried out in the form of budding, fragmentation, poly-embryony, etc. When budding, the hydra forms a protrusion of the body wall, which gradually increases in size, and a mouth opening breaks through at the anterior end, surrounded by tentacles. It ends with the formation of a small hydra, which then separates 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 full-fledged individuals develop (jellyfish, sea anemones, flat and annelids, echinoderms).

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

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

Asexual reproduction requires only one parent, which saves the time and energy required to find a sexual partner. In addition, new individuals can arise from each fragment of the maternal organism, which is also a saving of matter and energy spent on reproduction. The rate of asexual reproduction is also quite high; for example, bacteria are able to divide every 20-30 minutes, increasing their numbers extremely quickly. With this method of reproduction, genetically identical descendants are formed - clones, which can be considered as an advantage provided that environmental conditions are maintained constant.

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

Sexual reproduction- a method of reproduction in which the formation and fusion of 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 (in humans 2n = 46) merged, then already in the second generation the cells of the new organism would already contain a tetraploid set (in humans 4n = 92), in the third - octaploid, etc. .

However, the dimensions of a eukaryotic cell are not unlimited; they should fluctuate between 10-100 microns, since with smaller cell sizes it will not contain the full set of substances and structures necessary for its life, and with large sizes the uniform supply of the cell with oxygen, carbon dioxide, water and other necessary substances will be disrupted. Accordingly, the size of the nucleus in which the chromosomes are located cannot exceed 1/5-1/10 of the volume of the cell, and if these conditions are violated, the cell will no longer be able to exist. Thus, for sexual reproduction, a preliminary reduction in the number of chromosomes is necessary, which will be restored during fertilization, which is ensured by the process of meiotic cell division.

The reduction in the number of chromosomes must also be strictly ordered and equivalent, since if the new organism does not have complete pairs of chromosomes with their overall normal number, then it either will not be viable, or this will be accompanied by the development of serious diseases.

Thus, meiosis ensures a decrease in the number of chromosomes, which is restored during fertilization, maintaining the overall 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, as in daphnia, honey bees and some rock lizards. Sometimes this process is stimulated by the introduction of sperm from organisms of another species.

In the process of conjugation, which is characteristic, for example, of ciliates, individuals exchange fragments of hereditary information and then reproduce asexually. Strictly speaking, conjugation is a sexual process and 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 reproductive cells are produced by different individuals are called dioecious, whereas those capable of producing both types of gametes - hermaphrodites. Hermaphroditism is characteristic of many flat and annelid worms and gastropods.

Plants in which male and female flowers or other opposite sexual 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 better adaptation of descendants to the environment, their survival and a greater likelihood of transmitting their hereditary information to subsequent generations. This process leads to changes in the characteristics and properties of organisms and, ultimately, to the formation of new species in the process of evolutionary natural selection.

At the same time, matter and energy are used inefficiently during sexual reproduction, since organisms are often forced to produce millions of gametes, but only a few of them are used during fertilization. In addition, energy has to be spent on providing other conditions. For example, plants form flowers and produce nectar to attract animals, which transfer pollen to the female parts of other flowers, and animals spend a lot of time and energy searching for mates and courtship. Then you have to spend a lot of energy caring for the offspring, because when sexual reproduction occurs, the offspring are often so small at first that many of them die from predators, starvation, or simply due to unfavorable conditions. Consequently, with asexual reproduction, energy expenditure is 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, crop production and other areas to develop new plant varieties and animal breeds, preserve economically valuable traits, and quickly increase the number of individuals.

In asexual propagation of plants, along with traditional methods - cuttings, grafting and propagation by layering, modern methods associated with the use of tissue culture are gradually occupying a leading position. In this case, new plants are obtained from small fragments of the mother plant (cells or pieces of tissue) grown on a nutrient medium containing all the nutrients and hormones necessary for the plant. These methods make it possible not only to quickly propagate plant varieties with valuable traits, such as potatoes resistant to leafroll virus, but also to obtain organisms uninfected by viruses and other plant pathogens. Tissue culture also underlies the production of so-called transgenic or genetically modified organisms, as well as the hybridization of somatic plant cells that cannot be crossed in any other way.

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

Since higher animals do not have the ability for natural asexual reproduction, their main method of reproduction is sexual. To do this, crossing individuals of both the same species (breed) and interspecific hybridization are used, which produces such well-known hybrids as a mule and a hinny, depending on which species were taken as mothers - a donkey and a horse. However, interspecific hybrids are often sterile, that is, unable to produce offspring, so they must be bred anew each time.

Artificial parthenogenesis is also used to reproduce farm animals. The outstanding Russian geneticist B.L. Astaurov, by increasing the temperature, caused a greater yield of female silkworms, who weave cocoons from a thinner and more valuable thread than males.

Cloning can also be considered asexual reproduction, since it uses the nucleus of a somatic cell, which is introduced into a fertilized egg with a killed nucleus. The developing organism must be a copy, or clone, of an already existing organism.

Fertilization in flowering plants and vertebrates

Fertilization is the process of fusion of male and female germ cells to form a zygote.

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

Most often in nature, fertilization occurs with the male reproductive cells of another organism, but in a number of cases penetration of one’s own sperm is also possible - self-fertilization. From an evolutionary point of view, self-fertilization is less beneficial, since in this case the probability of the emergence of new gene combinations is minimal. Therefore, even in most hermaphroditic organisms, cross-fertilization occurs. This process is inherent in both plants and animals, but there are a number of differences in its course in the above-mentioned organisms.

Thus, in flowering plants, fertilization is preceded by pollination- transfer of pollen containing male reproductive cells - sperm - to 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 fuses with the central cell (2n), subsequently giving rise to the storage tissue of the secondary endosperm. This method of fertilization is called double fertilization(Fig. 3.4).

In animals, particularly vertebrates, fertilization is preceded by the convergence of gametes, or insemination. The success of insemination is facilitated by the synchronization of the release of male and female reproductive cells, as well as the release of specific chemicals by the eggs to facilitate the orientation of sperm in space.

When breeding cultivated plants and domestic animals, human efforts are mainly aimed at preserving and increasing economically valuable traits, while the resistance of these organisms to environmental conditions and viability in general are reduced. In addition, soybeans and many other crops are self-pollinating, so human intervention is necessary to develop new varieties. Difficulties may also arise in the fertilization process itself, since some plants and animals may have sterility genes.

In plants for breeding purposes, it is produced 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 prevent pollination by pollen of other plants. In some cases, artificial pollination is carried out to increase productivity, since seeds and fruits do not develop from the ovaries of unpollinated flowers. This technique was previously practiced in sunflower crops.

With distant hybridization, especially if the plants differ in the number of chromosomes, natural fertilization either becomes completely impossible, or already at the first cell division, chromosome divergence is disrupted and the organism dies. In this case, fertilization is carried out under artificial conditions, and at the beginning of division the cell is treated with colchicine, a substance that destroys the spindle of division, while the chromosomes scatter throughout the cell, and then a new nucleus is formed with twice the number of chromosomes, and such problems do not arise during subsequent divisions. Thus, the radish-cabbage hybrid G.D. Karpechenko and triticale, a high-yielding hybrid of wheat and rye, were created.

Major species of farm animals have even more barriers to fertilization than plants, forcing humans to take drastic measures. Artificial insemination is used mainly when breeding valuable breeds of livestock, when it is necessary to obtain as many offspring as possible from one sire. In these cases, the seminal fluid is collected, mixed with water, placed in ampoules, and then, as necessary, introduced into the female genital tract. In fish farms, during artificial insemination of fish, male sperm 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 humans 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, a distinction is made between external and internal fertilization. At external fertilization female and male reproductive cells are brought out, where the process of their fusion occurs, as, for example, in annelids, bivalves, skullless mollusks, most fish and many amphibians. Despite the fact that it does not require the bringing together of breeding individuals, in mobile animals it is possible not only for them to come together, but also to gather together, as during the spawning of fish.

Internal fertilization is associated with the introduction of male reproductive products into the female’s reproductive tract, and an already fertilized egg is released. It often has dense membranes that prevent it from being damaged and the penetration of subsequent sperm. Internal fertilization is characteristic of the vast majority of terrestrial animals, for example, flatworms and roundworms, many arthropods and gastropods, reptiles, birds and mammals, as well as a number of amphibians. It is also found in some aquatic animals, including cephalopods and cartilaginous fish.

There is also an intermediate type of fertilization - external-internal, in which the female captures sexual products specially left by the male on some substrate, as happens in some arthropods and tailed amphibians. External-internal fertilization can be considered as transitional from external to internal.

Both external and internal fertilization have their advantages and disadvantages. Thus, during external fertilization, germ cells are released into water or air, as a result of which the vast majority of them die. However, this type of fertilization ensures the existence of sexual reproduction in such attached and sedentary animals as bivalves and skullless mollusks. During internal fertilization, the loss of gametes is, of course, much less, but in this case, matter and energy are spent on finding a partner, and the offspring that are born are often too small and weak and require long-term parental care.

3.3. Ontogenesis and its inherent patterns. Specialization of cells, formation of tissues and organs. Embryonic and postembryonic development of organisms. Life cycles and alternation of generations. Causes of disturbances in the development of organisms.

Ontogenesis and its inherent patterns

Ontogenesis(from Greek ontos- existing and genesis- emergence, origin) is the process of individual development of an organism from birth to death. This term was introduced in 1866 by the German scientist E. Haeckel (1834-1919).

The birth of an organism is considered to be the appearance of a zygote as a result of fertilization of an egg by a sperm, although during parthenogenesis a zygote as such is not formed. During the process of ontogenesis, growth, differentiation and integration of parts of the developing organism occur. Differentiation(from lat. differential- difference) is the process of the emergence 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 Greek embryo- embryo and logo- word, science). A significant contribution to its development was made by Russian scientists K. Baer (1792-1876), who discovered the mammalian egg 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 characteristics 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 ontogenesis is determined by genetic programs fixed in the process of evolution, that is, ontogenesis is a brief repetition of the historical development of a given species, or phylogeny.

Despite the inevitable switching of individual groups of genes during individual development, all changes in the body occur gradually and do not violate its integrity, however, the events of each previous stage have a significant impact on the course of subsequent stages of development. Thus, any disruptions in the development process can lead to an interruption of the process of ontogenesis at any stage, as happens quite often with embryos (so-called miscarriages).

Thus, the process of ontogenesis is characterized by the unity of space and time of action, since it is inextricably linked with the body of the individual and proceeds unidirectionally.

Embryonic and postembryonic development of organisms

Periods of ontogenesis

There are several periodizations of ontogenesis, but most often the embryonic and postembryonic periods are distinguished in the ontogenesis of animals.

Embryonic period begins with the formation of a zygote during the process of fertilization and ends with the birth of the organism or its release from the embryonic (egg) membranes.

Postembryonic period lasts from birth to death of the organism. Sometimes they isolate proembryonic period or progenesis, which includes gametogenesis and fertilization.

Embryonic development or embryogenesis, in animals and humans is divided into a number of stages: fragmentation, gastrulation, histogenesis and organogenesis, and period of differentiated embryo.

Splitting up is the process of mitotic division of the zygote into smaller and smaller cells - blastomeres (Fig. 3.5). First, two cells are formed, then four, eight, etc. The decrease in cell size is mainly due to the fact that in the interphase of the cell cycle, for various reasons, there is no Gj period, in which an increase in the size of daughter cells should occur. This process is similar to breaking ice, but is not chaotic, but strictly ordered. For example, in humans this fragmentation is bilateral, that is, bilaterally symmetrical. As a result of fragmentation and subsequent divergence 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 blastocoele.

Gastrulation called the process of formation of a two- or three-layer embryo - gastrula(from Greek gaster- stomach), which occurs immediately after the formation of the blastula. Gastrulation is carried out by the movement of cells and their groups relative to each other, for example, by invagination of one of the walls of the blastula. In addition to two or three layers of cells, the gastrula also has a primary mouth - blastopore.

The layers of gastrula cells are called germ layers. There are three germ layers: ectoderm, mesoderm and endoderm. Ectoderm(from Greek ectos- outside, outside and dermis- skin) is the outer germ layer, mesoderm(from Greek mesos- average, intermediate) - average, and endoderm(from Greek entos- inside) - internal.

Despite the fact that all cells of a developing organism originate from a single cell - the zygote - and contain the same set of genes, that is, they are its clones, since they are formed as a result of mitotic division, the 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 further determine the specific functions of the cell and leave an imprint on its structure.

The specialization of cells is influenced by the proximity of other cells, as well as the hormonal background. For example, if a fragment on which the notochord develops is transplanted from one frog embryo to another, this will cause the formation of the rudiment 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 skin epithelium and its derivatives (hair, nails, claws, feathers), oral epithelium and tooth enamel, rectum, nervous system, sensory organs, gills, etc. are formed from the ectoderm. Derivatives of the endoderm are the intestines and related with it are 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, will reduce, from Greek. neuron- nerve). This process is also accompanied by the formation of a complex of axial organs, such as the notochord.

After organogenesis occurs, a period begins differentiated embryo which is characterized by continued specialization of body cells and rapid growth.

In many animals, during embryonic development, embryonic membranes and other temporary organs appear that are not useful in subsequent development, for example, the placenta, umbilical cord, etc.

The postembryonic development of animals according to their ability to reproduce is divided into pre-reproductive (juvenile), reproductive and post-reproductive periods.

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

The growth of the body 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 until the age of 13-15, although the final formation of the body occurs before the age of 25. Unlimited, or open growth continues throughout the life of the individual, as in plants and some fish. There are also periodic and non-periodic growth.

Growth processes are controlled by the endocrine or hormonal system: in humans, an increase in the linear size of the body is facilitated by the release of somatotropic hormone, while gonadotropic hormones largely suppress it. Similar mechanisms have been discovered in insects, which have a special juvenile hormone and a molting hormone.

In flowering plants, embryonic development occurs after double fertilization, in which one sperm fertilizes the egg, and the second fertilizes the central cell. The zygote produces an embryo that undergoes a series of divisions. After the first division, the embryo itself is formed from one cell, and the suspension is formed from the second, 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 (Fig. 3.7).

Embryonic and postembryonic development of seed plants are often separated in time because they require specific conditions for germination. The postembryonic period in plants is divided into vegetative, generative and aging periods. During the vegetative period, the biomass of the plant increases; during the generative period, they acquire the ability for sexual reproduction (in seed plants, for 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 developmental stages, starting from the zygote, after 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 in higher plants and animals the diploid set predominates, and in lower ones, vice versa.

Life cycles can be simple or complex. Unlike a simple life cycle, in a complex life cycle, sexual reproduction alternates with parthenogenetic and asexual reproduction. For example, Daphnia crustaceans, which produce asexual generations during the summer, reproduce sexually in the fall. The life cycles of some fungi are especially complex. In a number of animals, alternation of sexual and asexual generations occurs regularly, and this life cycle is called correct. It is characteristic, for example, of 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 annual and perennial.

Knowledge of life cycles is necessary for genetic analysis, since in the haploid and diploid states the action of genes is revealed differently: in the first case there is greater opportunity for the expression of all genes, while in the second some genes are not detected.

Causes of impaired development of organisms

The ability to self-regulate and resist harmful environmental influences does not arise immediately in organisms. During embryonic and postembryonic development, when many of the body's defense systems have not yet been 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 body itself. It is either equipped with special nourishing tissue or receives nutrients directly from the mother's body. However, changes in external conditions can speed up or slow down the development of the embryo and even cause various disorders.

Factors that cause deviations in the development of the embryo are called teratogenic, or teratogens. Depending on the nature of these factors, they are divided into physical, chemical and biological.

TO physical factors This includes, first of all, ionizing radiation, which provokes numerous mutations in the fetus that may be incompatible with life.

Chemical teratogens are heavy metals, benzopyrene emitted by cars and industrial enterprises, phenols, series medicines, alcohol, drugs and nicotine.

Parental use of alcohol, drugs, and smoking tobacco has a particularly harmful effect on the development of the human embryo, since alcohol and nicotine inhibit cellular respiration. Insufficient supply of oxygen to the embryo leads to the fact that fewer cells are formed in the developing organs, and the organs are underdeveloped. Nerve tissue is especially sensitive to lack of oxygen. The future mother's use of alcohol, drugs, smoking tobacco, 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 properties of organisms. Basic genetic concepts.

Genetics, its tasks

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 relevant evidence. Even the theory of intracellular pangenesis formulated by H. de Vries in 1889, which assumed the existence in the cell nucleus of certain “pangenes” that determine the hereditary inclinations of the organism, and the release into protoplasm of only those of them that determine the type of cell, could not change the situation, as well as the theory of “germ plasm” by A. Weissman, according to which characteristics acquired during the process of ontogenesis are not inherited.

Only the works of the Czech researcher G. Mendel (1822-1884) became the foundation stone of modern genetics. However, despite the fact that his works were cited in scientific publications, his contemporaries did not pay attention to them. And only the rediscovery of the patterns of independent inheritance by three scientists at once - E. Chermak, K. Correns and X. de Vries - forced the scientific community to turn to the origins of genetics.

Genetics is a science that studies the patterns of heredity and variability and methods of managing them.

The tasks of genetics at the present stage are the study of qualitative and quantitative characteristics of hereditary material, analysis of the structure and functioning of the genotype, deciphering the fine structure of the gene and methods for regulating gene activity, searching for genes that cause the development of hereditary human diseases and methods for “correcting” them, creating a new generation of drugs according to the type DNA vaccines, the construction, using genetic and cellular engineering, of organisms with new properties that could produce the medicines and food products needed by humans, as well as the complete deciphering of the human genome.

Heredity and variability - properties of organisms

Heredity is the ability of organisms to transmit their characteristics and properties over a series of generations.

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

Signs- these are any morphological, physiological, biochemical and other characteristics of organisms by which some of them differ from others, for example eye color. Properties also called any functional characteristics of organisms, which are based on a certain structural characteristic or group of elementary characteristics.

The characteristics 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 colors, while quantitative ones (milk yield of cows, wheat yield) do not have clearly defined differences.

The material carrier of heredity is DNA. In eukaryotes, there are two types of heredity: genotypic And cytoplasmic. The carriers of genotypic heredity are localized in the nucleus and will be discussed further, while the carriers of cytoplasmic heredity are the circular DNA molecules located in mitochondria and plastids. Cytoplasmic heredity is transmitted mainly with the egg, therefore it is also called maternal.

A small number of genes are localized in the mitochondria of human cells, but their changes can have a significant impact on the development of the organism, for example, leading to the development of blindness or a gradual decrease in mobility. Plastids play an equally important role in plant life. Thus, in some areas of the leaf, chlorophyll-free cells may be present, which leads, on the one hand, to a decrease in plant productivity, and on the other hand, such variegated organisms are valued in decorative landscaping. Such specimens reproduce mainly asexually, since sexual reproduction often produces ordinary green plants.

Genetics methods

The hybridological method, or crossbreeding method, consists of selecting parental individuals and analyzing the offspring. In this case, the genotype of an organism is judged by the phenotypic manifestations of genes in descendants obtained through a certain crossing scheme. This is the oldest informative method of genetics, which was most fully first used 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 organism’s chromosomes. The study of these features allows us to identify various developmental pathologies.

The biochemical method makes it possible 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 DNA sections under study. They make it possible to identify genes for hereditary diseases even in embryos, establish paternity, etc.

The population statistical method allows us to determine the genetic composition of a population, the frequency of certain genes and genotypes, genetic load, and also outline the prospects for the development of a 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 different organisms, for example, a mouse and a hamster, a mouse and a human, etc.

Basic genetic concepts and symbolism

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

Some genes can influence the manifestation of several traits at once. This phenomenon is called pleiotropy. For example, the gene that causes the development of the hereditary disease arachnodactyly (spider fingers) causes curvature of the lens and pathologies of many internal organs.

Each gene occupies a strictly defined place on the chromosome - locus Since in the somatic cells of most eukaryotic organisms the chromosomes are paired (homologous), each of the paired chromosomes contains one copy of the gene responsible for a certain trait. Such genes are called allelic.

Allelic genes most often exist in two versions - dominant and recessive. Dominant called an allele that manifests itself regardless of which gene is located on the other chromosome and suppresses the development of the trait encoded by the recessive gene. Dominant alleles are usually designated in capital letters Latin alphabet (A, B, C and etc.), and recessive ones - lowercase (a, b, With and etc.)- Recessive alleles can only be expressed if they occupy loci on both paired chromosomes.

An organism that has the same alleles on both homologous chromosomes is called homozygous for this gene, or homozygous ( AA , aa, AABB,aabb etc.), and an organism in which both homologous chromosomes contain different gene variants - dominant and recessive - is called heterozygous for this gene, or heterozygote (Aa, AaBb etc.).

A number of genes may 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 of a pair carries only one allele, that is, all three gene variants cannot be represented in one organism.

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 characteristics and properties of an organism, which is the result of the interaction of the genotype and the environment.

Since organisms differ from each other in many traits, the patterns of their inheritance can only be established by analyzing two or more traits in the offspring. Crossing, in which inheritance is considered and an accurate quantitative count of the offspring is carried out according to one pair of alternative characteristics, is called monohybrid, in two pairs - dihybrid, according to more signs - polyhybrid.

Based on the phenotype of an individual, it is not always possible to determine its genotype, since both an organism homozygous for the dominant gene (AA) and heterozygous (Aa) will have a manifestation of the dominant allele in the phenotype. Therefore, to check the genotype of an organism with cross-fertilization, they use test cross- crossbreeding, in which an organism with a dominant trait is crossed with one homozygous for a recessive gene. In this case, an organism homozygous for the dominant gene will not produce splitting in the offspring, whereas in the offspring of heterozygous individuals there is an equal number of individuals with dominant and recessive traits.

The following conventions are most often used to record crossing schemes:

R (from lat. parenta- parents) - parent organisms;

♀ (alchemical sign of Venus - mirror with handle) - maternal individual;

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

x - crossing sign;

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

F a - offspring from an 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. Satton independently suggested that the behavior of chromosomes during cell maturation and fertilization makes it possible to explain the splitting of hereditary factors according to Mendel, i.e., in their opinion, genes must be located on chromosomes. These assumptions became the cornerstone of the chromosomal theory of heredity.

In 1906, English geneticists W. Bateson and R. Punnett discovered a violation of Mendelian segregation when crossing sweet peas, and their compatriot L. Doncaster, in experiments with the gooseberry moth butterfly, discovered sex-linked inheritance. The results of these experiments clearly contradicted Mendelian ones, but if we consider that by that time it was already known that the number of known characteristics for experimental objects far exceeded the number of chromosomes, and this suggested the idea that each chromosome carries more than one gene, and the genes of one chromosome are inherited together.

In 1910, experiments by T. Morgan's group began on a new experimental object - the fruit fly Drosophila. The results of these experiments made it possible by the mid-20s of the 20th century to formulate the basic principles of the chromosomal theory of heredity, to determine the order of genes in chromosomes and the distances between them, i.e., to draw up the first maps of chromosomes.

Basic provisions of the chromosomal theory of heredity:

1) Genes are located on chromosomes. Genes on the same chromosome are inherited together, or linked, and are called clutch group. The number of linkage groups is numerically equal to the haploid set of chromosomes.

Each gene occupies a strictly defined place on the chromosome - a locus.

Genes on 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 typical only for genes on non-homologous chromosomes.

Modern ideas about the gene and genome

In the early 40s of the 20th century, J. Beadle and E. Tatum, analyzing the results of genetic studies conducted on the neurospora fungus, came to the conclusion that each gene controls the synthesis of an enzyme, and formulated the principle of “one gene - one enzyme” .

However, already in 1961 F. Jacob, J.-L. Monod and A. Lvov managed to decipher the structure of the E. coli gene and study the regulation of its activity. For this discovery they were awarded the Nobel Prize in Physiology or Medicine in 1965.

In the process of research, 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.

Structure of a prokaryotic gene. The structural gene of prokaryotes has a complex structure, since it includes regulatory regions and coding sequences. The regulatory regions include the promoter, operator and terminator (Fig. 3.8). Promoter called the region of the gene to which the enzyme RNA polymerase is attached, which ensures the synthesis of mRNA during transcription. WITH operator, located between the promoter and the structural sequence, can bind repressor protein does not allow RNA polymerase to begin reading the hereditary information from the coding sequence, and only its removal allows transcription to begin. The structure of the repressor is usually encoded in a regulatory gene located in another part of the chromosome. Reading of information ends at a section of the gene called terminator.

Coding sequence A structural gene contains information about the amino acid sequence of the corresponding protein. The coding sequence in prokaryotes is called cistronome, and the totality of coding and regulatory regions of a prokaryotic gene - operon. In general, prokaryotes, which include E. coli, have a relatively small number of genes located on a single circular chromosome.

The cytoplasm of prokaryotes may also contain additional small circular or open DNA molecules called plasmids. Plasmids are able to integrate into chromosomes and be transmitted from one cell to another. They may carry information about sex characteristics, pathogenicity and antibiotic resistance.

Structure of a 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 eukaryotic genes significant regions ( exons) alternate with insignificant ones ( introns), which are completely transcribed into mRNA and then excised during their maturation. The biological role of introns is to reduce the likelihood of mutations in significant regions. The regulation of genes in eukaryotes is much more complex than that described for prokaryotes.

Human genome. In each human cell, the 46 chromosomes contain about 2 m of DNA, tightly packed into a double helix, which consists of approximately 3.2 x 10 9 nucleotide pairs, providing about 10 1900000000 possible unique combinations. By the end of the 80s of the 20th century, the location of approximately 1,500 human genes was known, but their total number was estimated at approximately 100 thousand, since humans have approximately 10 thousand hereditary diseases alone, not to mention the number of various proteins contained in cells .

In 1988, the international Human Genome project was launched, which by the beginning of the 21st century ended with a complete decoding of the nucleotide sequence. He made it possible to understand that two different people have 99.9% similar nucleotide sequences, and only the remaining 0.1% determine our individuality. In total, approximately 30-40 thousand structural genes were discovered, but then their number was reduced to 25-30 thousand. Among these genes there are not only unique ones, but also repeated hundreds and thousands of times. However, these genes encode a much larger number of proteins, for example tens of thousands of protective proteins - immunoglobulins.

97% of our genome is genetic “junk” that exists only because it can reproduce well (RNA that is transcribed in these regions never leaves the nucleus). For example, among our genes there are not only “human” genes, but also 60% of genes similar to the genes of the Drosophila fly, and up to 99% of our genes are similar to chimpanzees.

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

Decoding the human genome has not yet given a direct effect, since we have received a kind of instruction for assembling such a complex organism as a person, but have not learned how to manufacture it or at least correct errors in it. Nevertheless, the era of molecular medicine is already on the threshold; all over the world, so-called gene preparations are being developed that can block, delete 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 genes in mitochondria and plastids has much in common with the organization of the prokaryotic genome. Despite the fact that these organelles carry less than 1% of the cell's hereditary information and do not even encode the full set of proteins necessary for their own functioning, they are capable of significantly influencing some of the body's characteristics. Thus, variegation in plants of chlorophytum, ivy and others is inherited by a small number of descendants even when crossing two variegated plants. This is due to the fact that plastids and mitochondria are transmitted mostly with the cytoplasm of the egg, therefore such heredity is called maternal, or cytoplasmic, in contrast to genotypic, which is localized in the nucleus.

3.5. Patterns of heredity, their cytological basis. Mono- and dihybrid crossing. Patterns of inheritance established by G. Mendel. Linked inheritance of traits, disruption of gene linkage. 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. Human genome. Gene interaction. Solving genetic problems. Drawing up crossing schemes. G. Mendel's laws and their cytological foundations.

Patterns of heredity, their cytological basis

According to the chromosomal theory of heredity, each pair of genes is localized in a pair of homologous chromosomes, and each chromosome carries only one of these factors. If we imagine that genes are point objects on straight chromosomes, then schematically homozygous individuals can be written as A||A or a||a, whereas heterozygous - A||a. When gametes are formed during the process of meiosis, each of the genes of a heterozygote pair will end up in one of the germ cells (Fig. 3.9).

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

In cases where genes are located on different chromosomes, then during the formation of gametes, the distribution between them of alleles from a given pair of homologous chromosomes occurs completely independently of the distribution of alleles from other pairs (Fig. 3.11). It is the random arrangement of homologous chromosomes at the spindle equator in metaphase I of meiosis and their subsequent divergence in anaphase I that leads to a variety of recombinations of alleles 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 a haploid set. In humans, n = 23, and the possible number of combinations is 2 23 = 8388608. The subsequent combination of gametes during fertilization is also random, and therefore independent segregation for each pair of characters can be recorded in the offspring (Fig. 3.11).

However, the number of characteristics 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 some individual, heterozygous for two pairs of genes located on homologous chromosomes, produces gametes, then we should take into account not only the probability of the formation of gametes with the original chromosomes, but also gametes that received chromosomes changed as a result of crossing over in prophase I of meiosis. Consequently, new combinations of traits will arise in the offspring. Data obtained in experiments on Drosophila formed the basis chromosomal theory of heredity.

Other fundamental confirmation of the cytological basis of heredity was obtained from the study of various diseases. Thus, in humans, one form of cancer is caused by the loss of a small section of one of the chromosomes.

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

The basic patterns of independent inheritance of traits were discovered by G. Mendel, who achieved success by using a new hybridological method in his research at that time.

The success of G. Mendel was ensured by the following factors:

1. a good choice of the object of study (peas), which has a short growing season, is a self-pollinating plant, produces a significant number of seeds and is represented by a large number of varieties with clearly distinguishable characteristics;

2. using only pure lines of peas, which for several generations did not produce splitting of traits in the offspring;

3. concentration on only one or two characteristics;

4. planning the experiment and drawing up clear crossing schemes;

5. accurate quantitative calculation of the resulting offspring.

For the study, G. Mendel selected only seven traits that had 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 when studying other signs (Table 3.1). The traits that predominated in the first generation were called by G. Mendel dominant. Those of them that did not appear in the first generation were called recessive.

Individuals that produced cleavage in their offspring were called heterozygous, and individuals that did not split - homozygous.

Table 3.1

Traits of peas, the inheritance of which was studied by G. Mendel

A cross in which the manifestation of only one trait is studied is called monohybrid. In this case, patterns of inheritance of only two variants of one trait can be traced, the development of which is determined by a pair of allelic genes. For example, the trait “flower corolla color” in peas has only two manifestations - red and white. All other characteristics 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:

Having crossed 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 as the father. The same results were obtained in crosses for other characteristics, which gave G. Mendel grounds to formulate law of uniformity of first generation hybrids, which is also called Mendel's first law And law of dominance.

Mendel's first law:

When crossing homozygous parental forms that differ in one pair of alternative traits, all hybrids of the first generation will be uniform in both genotype and phenotype.

A - yellow seeds; a - green seeds.

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

Mendel's second law:

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

However, from the phenotype of an individual it is not always possible to determine its genotype, since as homozygotes for the dominant gene (AA), and heterozygotes (Ah) will have a manifestation of a dominant gene in their phenotype. Therefore, for organisms with cross-fertilization, they use test cross- a cross in which an organism with an unknown genotype is crossed with a homozygote for a recessive gene to test the genotype. At the same time, homozygous individuals for the dominant gene do not produce segregation 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 do not mix during the formation of hybrids, but remain unchanged. Since the connection between generations is carried out through gametes, he assumed that in the process of their formation, only one factor from the pair enters each of the gametes (i.e., the gametes are genetically pure), and upon 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, i.e., each gamete carries only one variant of the gene.

However, organisms differ from each other in many traits, so it is possible to establish patterns of their inheritance only by analyzing two or more traits in the offspring. Crossing, in which inheritance is considered and an accurate quantitative account of the offspring is made according to two pairs of characteristics, is called dihybrid. If the manifestation of a larger number of hereditary characteristics is analyzed, then this is already polyhybrid crossing.

Dihybrid crossing scheme:

With a greater variety of gametes, determining the genotypes of descendants becomes difficult, so the Punnett grid is widely used for analysis, into which male gametes are entered horizontally and female gametes vertically. The genotypes of the offspring are determined by the combination of genes in the columns and rows.

For dihybrid crossing, G. Mendel chose two characteristics: 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 seeds and 32 green wrinkled ones. Calculations showed that the split was close to 9:3:3:1, but for each of the characteristics the ratio was maintained at 3:1 (yellow - green, smooth - wrinkled). This pattern is called law of independent splitting of characteristics, 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 there will be an independent splitting of these traits in a ratio of 3:1 (9:3:3:1 in a dihybrid crossing).

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

T. Morgan's laws: linked inheritance of traits, disruption of gene linkage

The new organism receives from its parents not a scattering of genes, but entire chromosomes, and the number of traits and, accordingly, the genes that determine them is much greater than the number of chromosomes. According to the chromosomal theory of heredity, genes located on the same chromosome are inherited linked. As a result, during dihybrid crossing they do not give the expected 9:3:3:1 split 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 hybrids of the first generation, the splitting should be 1:1.

To test this assumption, the American geneticist T. Morgan selected 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 were also a small number of individuals with new combinations of these characters ( Fig. 3.12).

These individuals are called recombinant. However, after analyzing the crossing of first-generation hybrids with homozygotes for recessive genes, T. Morgan discovered that 41.5% of individuals had a gray body and long wings, 41.5% had a black body and rudimentary wings, 8.5% had a gray body and rudimentary wings, and 8.5% - black body and rudimentary wings. He associated the resulting splitting with crossing over occurring in prophase I of meiosis and proposed to consider 1% crossing over, subsequently named after him as a morganid, as a unit of distance between genes on a chromosome.

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

Morgan's Law:

Genes localized on the same chromosome occupy a specific place called a locus and are inherited linked, with the strength of linkage inversely proportional to the distance between genes.

Genes located on the chromosome directly next to each other (the probability of crossing over is extremely low) are called fully linked, and if there is at least one more gene between them, then they are not completely linked and their linkage is broken during crossing over as a result of the exchange of sections of homologous chromosomes.

The phenomena of gene linkage and crossing over make it possible to construct maps of chromosomes with the order of gene arrangement marked on them. Genetic maps of chromosomes have been created for many genetically well-studied objects: fruit flies, mice, humans, corn, wheat, peas, etc. The study of genetic maps allows us to compare the genome structure of different species of organisms, which is important for genetics and selection, as well as evolutionary studies .

Genetics of sex

Floor- this is a set of morphological and physiological characteristics of an organism that ensure sexual reproduction, the essence of which comes down to fertilization, that is, the fusion of male and female germ cells into a zygote, from which a new organism develops.

The characteristics by which one sex differs from the other are divided into primary and secondary. Primary sexual characteristics include the genitals, and all others are secondary.

In humans, secondary sexual characteristics are body type, timbre of voice, predominance of muscle or fat tissue, presence of facial hair, Adam's apple, and mammary glands. Thus, in women, the pelvis is usually wider than the shoulders, adipose tissue predominates, the mammary glands are pronounced, and the voice is high. Men are more different from them broad shoulders, predominance of muscle tissue, the presence of hair on the face and Adam's apple, as well as a low voice. Humanity has long been interested in the question of why males and females are born in a ratio of approximately 1:1. An explanation for this was obtained by studying the karyotypes of insects. It turned out that the females of some bugs, grasshoppers and butterflies have one more chromosome than the males. In turn, males produce gametes that differ in the number of chromosomes, thereby predetermining the sex of the offspring. However, it was subsequently found that in most organisms the number of chromosomes in males and females still does not differ, but one of the sexes has a pair of chromosomes that do not fit each other in size, while the other has all the chromosomes in pairs.

A similar difference was also found in the human karyotype: men have two unpaired chromosomes. In shape, these chromosomes at the beginning of division resemble the Latin letters X and Y, and therefore were called X- and Y-chromosomes. 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, whereas sex chromosomes- these are chromosomes that differ between sexes and carry information about sexual characteristics. In cases where a sex carries the same sex chromosomes, for example XX, it is said to homozygous or homogametic(forms identical gametes). The other sex, having different sex chromosomes (XY), is called hemizygous(not having a full equivalent of allelic genes), or heterogametic. In humans, most mammals, the Drosophila fly and other organisms, the female sex is homogametic (XX) and the male sex is heterogametic (XY), while in birds the male sex is homogametic (ZZ, or XX), and the female sex is heterogametic (ZW, or XY) .

The X chromosome is a large unequal-armed chromosome that carries over 1,500 genes, and many of their mutant alleles cause severe hereditary diseases in humans, such as hemophilia and color blindness. The Y chromosome, on the contrary, is very small, it contains only about a dozen genes, including specific genes responsible for male development.

A man's karyotype is written as ♂46, XY, and a woman's karyotype is written as ♀ 46, XX.

Since gametes with sex chromosomes are produced in males with equal probability, the expected sex ratio in the offspring is 1:1, which coincides with what is actually observed.

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

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

Inheritance of sex-linked traits

Since some genes are located on sex chromosomes, which are not the same in representatives of opposite sexes, the nature of inheritance of traits encoded by these genes differs from the general one. This type of inheritance is called cris-cross inheritance because males inherit traits from their mother and females from their father. Traits determined by genes found on sex chromosomes are called adhered to the floor. Examples of sex-linked traits are the recessive traits of hemophilia and color blindness, which mainly affect males because there are no allelic genes on the Y chromosome. Women suffer from such diseases only if they received such signs from both their father and mother.

For example, if the mother was a heterozygous carrier of hemophilia, then in half of her sons blood clotting will be impaired: X n - normal blood clotting X h- blood incoagulability (hemophilia)

Traits encoded in the genes of the Y chromosome are transmitted purely through the male line and are called holandric(presence of membranes between the toes, increased hair growth on 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 the night beauty, when crossing plants with red and white corollas, the first generation hybrids have pink corollas, 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 believe that allelic genes may have a certain influence on each other. Subsequently, it was also found that non-allelic genes promote 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. Currently, the interaction of allelic and non-allelic genes is distinguished.

The interaction of allelic genes includes complete and incomplete dominance, codominance and overdominance. Complete dominance consider all cases of interaction of allelic genes in which the heterozygote exhibits an exclusively dominant trait, such as the color and shape of a seed in peas.

Incomplete dominance- this is a type of interaction of allelic genes in which the manifestation of a recessive allele to a greater or lesser extent weakens the manifestation of a dominant one, as in the case of the color of the corolla of the night beauty (white + red = pink) and wool in cattle.

Co-dominance call this type of interaction of allelic genes in which both alleles appear without weakening the effects of each other. A typical example of codominance is the inheritance of blood groups according to the ABO system (Table 3.2). IV (AB) blood 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 a dominant trait is manifested much more strongly than in a homozygous state; overdominance is often used in breeding and is considered a cause heterosis- phenomena of hybrid power.

A special case of interaction of allelic genes can be considered the so-called lethal genes, which in the homozygous state lead to the death of the organism most often in the embryonic period. The cause of the death of the offspring is the pleiotropic effect of the genes for gray coat color in astrakhan sheep, platinum color in foxes and the absence of scales in mirror carp. When crossing two individuals heterozygous for these genes, the segregation for the studied trait in the offspring will be 2:1 due to the death of 1/4 of the offspring.

The main types of interaction of non-allelic genes are complementarity, epistasis and polymerization. Complementarity- this is a type of interaction of non-allelic genes, in which the presence of at least two dominant alleles of different pairs is necessary for the manifestation of a certain state of a trait. For example, in pumpkin, when crossing plants with spherical (AAbb) and long (aaBB) plants with disc-shaped fruits appear in the first generation (AaBb).

TO epistasis include such phenomena of interaction of non-allelic genes, in which one non-allelic gene suppresses the development of the trait of another. For example, in chickens, plumage color is determined by one dominant gene, while another dominant gene suppresses color development, resulting in most chickens having white plumage.

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

Genotype as complete system

The genotype is not a mechanical sum of genes, since the possibility of a gene’s manifestation and the form of its manifestation depend on environmental conditions. IN in this case By environment we mean not only the environment, but also the genotypic environment - other genes.

The manifestation of qualitative traits rarely depends on environmental conditions, although if you shave an area of ​​the body with white hair on an ermine rabbit and apply an ice pack to it, then over time black hair will grow in this place.

The development of quantitative traits is much more dependent on environmental conditions. For example, if modern varieties of wheat are cultivated without the use of mineral fertilizers, then its yield will differ significantly from the genetically programmed 100 or more centners per hectare.

Thus, only the “abilities” of the organism are recorded in the genotype, but they manifest themselves only in interaction with environmental conditions.

In addition, genes interact with each other and, once in the same genotype, can greatly influence the manifestation of the action of neighboring genes. Thus, for each individual gene there is a genotypic environment. It is possible that the development of any trait is associated with the action of many genes. In addition, the dependence of several traits on one gene was revealed. For example, in oats, the color of the scales and the length of the seed awn are determined by one gene. In Drosophila, the gene for white eye color simultaneously affects the color of the body and internal organs, the length of the wings, decreased fertility and reduced life expectancy. It is possible that each gene is simultaneously the main action gene for “its” trait and a modifier for other traits. Thus, a phenotype is the result of the interaction of genes of the entire genotype with the environment during the ontogenesis 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, and only those organisms survived in which the interaction of genes gave the most favorable reaction in ontogenesis.

Human genetics

For humans 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 applied science, since it studies hereditary human diseases, of which more than 4 thousand have now been described. It stimulates the development of modern areas of general and molecular genetics, molecular biology and clinical medicine. Depending on the problems, human genetics is divided into several areas that have developed into independent sciences: genetics of normal human characteristics, medical genetics, genetics of behavior and intelligence, human population genetics. In this regard, in our time, man 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 characteristics and small pedigrees, the impossibility of creating identical and strictly controlled conditions for the development of descendants from different marriages, comparatively large number poorly differentiated chromosomes and the impossibility of experimentally obtaining mutations.

Methods for studying human genetics

The methods used in human genetics are not fundamentally different from those generally accepted for other objects - these are genealogical, twin, cytogenetic, dermatoglyphic, molecular biological And population statistical methods, somatic cell hybridization method And modeling method. Their use in human genetics takes into account the specifics of a person as a genetic object.

Twin method helps determine the contribution of heredity and the influence of environmental conditions on the manifestation of a trait based on an analysis of the coincidence of these traits in identical and fraternal twins. Thus, most identical twins have the same blood type, eye and hair color, as well as a number of other characteristics, while both types of twins suffer from measles at the same time.

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

Genealogical method is a method of compiling pedigrees, with the help of which the nature of inheritance of the studied characteristics, including hereditary diseases, is determined, and the birth of descendants with the corresponding characteristics is predicted. It made it possible to identify the hereditary nature of diseases such as hemophilia, color blindness, Huntington's chorea, etc. even before the discovery of the basic laws of heredity. When compiling pedigrees, records are kept about each family member and the degree of relationship between them is taken into account. Next, based on the data obtained, a family tree is built using special symbols (Fig. 3.13).

The genealogical method can be used on one family if there is information about a sufficient number of direct relatives of the person whose pedigree is being compiled - proband,- on the paternal and maternal lines, otherwise information is collected about several families in which this trait appears. The genealogical method makes it possible to establish not only the heritability of a trait, but also the nature of inheritance: dominant or recessive, autosomal or sex-linked, etc. Thus, based on the portraits of the Austrian Habsburg monarchs, the inheritance of prognathia (a strongly protruded lower lip) and “royal hemophilia” was established. 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. Calculation problems.

2. Problems to determine the genotype.

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

Feature calculation problems is the availability of information about the inheritance of the trait and the phenotypes of the parents, from which it is easy to determine the genotypes of the parents. They require establishing the genotypes and phenotypes of the offspring.

TOPIC 2. SOCIO-BIOLOGICAL FOUNDATIONS OF PHYSICAL CULTURE

Introduction

1.Organism as a biological system.

2.Anatomy – morphological features of the body.

3. The skeletal system and its functions.

4. Muscular system and its functions.

5. Digestive and excretory organs.

6. Physiological systems of the body.

7.Human motor activity and the relationship between physical and mental activity.

8. Physical education means that provide resistance to mental and physical performance.

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

10. Metabolism and energy.

11. Test questions.

Introduction

Socially – biological basis physical culture - these are the principles of interaction of social and biological laws in the process of a person mastering the values ​​of physical culture.

Man obeys biological laws inherent in all living beings. However, it differs from representatives of the animal world not only in structure, but also in developed thinking, intelligence, speech, and the characteristics of social and living conditions and social relationships. Labor and the influence of the social environment in the process of human development have influenced the biological characteristics of the modern human body and its environment. An organism is a coherent, unified self-regulating and self-developing biological system, the functional activity of which is determined by the interaction of mental, motor and autonomic reactions to environmental influences, which can be both beneficial and detrimental to health. A distinctive feature of a person is a conscious and active influence on external natural and social conditions that determine the state of people’s health, their performance, life expectancy and fertility (reproduction). Without knowledge about the structure of the human body, about the patterns of functioning of individual organs and systems of the body, about the peculiarities of the complex processes of its life, it is impossible to organize the process of forming a healthy lifestyle and physical training of the population, including students. Achievements of medical and biological sciences underlie the pedagogical principles and methods of the educational and training process, the theory and methodology of physical education and sports training.

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 course of his future life. Finding himself in autonomous conditions after birth, the child grows rapidly, the weight, length and surface area of ​​his body increases. Human growth continues until approximately 20 years of age. Moreover, in girls the greatest intensity of growth is observed in the period from 10 to 13, and in boys from 12 to 16 years. An increase in body weight occurs almost in parallel with an increase in its length and stabilizes by 20-25 years.

It should be noted that over the past 100-150 years, early morphofunctional development of the body in children and adolescents has been observed in a number of countries. This phenomenon is called acceleration (lat. accelera-tio- acceleration).

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

The basis of the body’s vital activity is 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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