Organization levels living systems reflect subordination, hierarchy structural organization life; differ from each other in the complexity of the organization of the system (a cell is simpler in comparison with a multicellular organism or population).

Standard of living - this is the form and way of its existence (the virus exists in the form of a DNA or RNA molecule enclosed in a protein shell - the form of the existence of the virus. However, the properties of a living system the virus shows only when it enters the cell of another organism, where it multiplies - the way it exists).

THEMATIC ASSIGNMENTS

Part A

A1. The level at which the processes of biogenic migration of atoms are studied is called:

1) biogeocenotic
2) biosphere
3) population-species
4) molecular genetic

A2. At the population-species level, they study:

1) gene mutations
2) the relationship of organisms of the same species
3) organ systems
4) metabolic processes in the body

A3. Maintaining Relative Constancy chemical composition organism is called

1) metabolism
2) assimilation
3) homeostasis
4) adaptation

A4. The occurrence of mutations is associated with such a property of the organism as

1) heredity
2) variability
3) irritability
4) self-reproduction

A5. Which of the following biological systems forms the most high level life?

1) amoeba cell
2) smallpox virus
3) a herd of deer
4) nature reserve

A6. Pulling the hand away from a hot object is an example

1) irritability
2) ability to adapt
3) inheritance of traits from parents
4) self-regulation

A7. Photosynthesis, protein biosynthesis are examples

1) plastic metabolism
2) energy metabolism
3) nutrition and breathing
4) homeostasis

A8. Which of the terms is synonymous with the concept of "metabolism"?

1) anabolism
2) catabolism
3) assimilation
4) metabolism

Part B

IN 1. Select the processes studied at the molecular genetic level of life:

1) DNA replication
2) inheritance of Down's disease
3) enzymatic reactions
4) the structure of mitochondria
5) cell membrane structure
6) blood circulation

IN 2. Correlate the nature of the adaptation of organisms with the conditions to which they were developed.

Part C

C1. What adaptations of plants provide them with reproduction and resettlement?
C2. What is common and what are the differences between different levels of organization of life?

By the 1960s in biology there is an idea of ​​the levels organization of the living as a concrete expression of an increasingly complex orderlinessorganic world. Life on Earth is represented by organisms of a kindbuildings belonging to certain systematic groups (type), as well ascommunities of varying complexity (biogeocenosis, biosphere). In turn, organismscharacterized by organ, tissue, cellular and molecular organization.Each organism, on the one hand, consists of specialized subordinateorganization systems (organs, tissues, etc.), on the other hand, is itselfrelatively isolated unit in the composition of supraorganismal biologicalsystems (species, biogeocenoses and the biosphere as a whole). Levels of organization alivematter are presented in fig. one

Fig.1. Levels of organization of the living

On all of them, such properties of life as discreteness and integrity are manifested. The body consists of various components - organs, but at the same time, thanks to their interaction, it is integral. The view is also complete system, although it is formed by separate units - individuals, however, their interaction maintains the integrity of the species. The existence of life at all levels is provided by the structure of the lowest rank. For example, the nature of the cellular level of organization is determined by the subcellular and molecular levels; organismic - organ; tissue, cellular; specific - organismal, etc. It should be noted the great similarity of units of organization at the lower levels and the ever-increasing difference at the higher levels (Table 1).

Table 1

Characteristics of the levels of organization of the living

The world of wildlife is a collection of biological systems different levels organization and different subordination. They are in constant interaction. There are several levels of living matter:

Molecular- any living system, no matter how complex it is organized, manifests itself at the level of functioning of biological macromolecules: nucleic acids, proteins, polysaccharides, as well as important organic substances. From this level, the most important processes of the organism's vital activity begin: metabolism and energy conversion, transmission of hereditary information, etc. - the most ancient level of the structure of living nature, bordering on inanimate nature.

Cellular- a cell is a structural and functional unit, also a unit of reproduction and development of all living organisms living on Earth. There are no non-cellular life forms, and the existence of viruses only confirms this rule, since they can exhibit the properties of living systems only in cells.

Tissue- Tissue is a collection of cells similar in structure, united by the performance of a common function.

Organ- in most animals, an organ is a structural and functional combination of several types of tissues. For example, human skin as an organ includes epithelium and connective tissue, which together perform whole line functions among which the most significant is protective.

Organismic- a multicellular organism is an integral system of organs specialized to perform various functions. Differences between plants and animals in the structure and methods of nutrition. The relationship of organisms with the environment, their adaptability to it.

population-species- a set of organisms of the same species, united by a common habitat, creates a population as a system of a supra-organismal order. In this system, the simplest, elementary evolutionary transformations are carried out.

Biogeocenotic- biogeocenosis - a set of organisms of different species and varying complexity of organization, all environmental factors.

biospheric The biosphere is the highest level of organization of living matter on our planet, including all life on Earth. Thus, living nature is a complexly organized hierarchical system.

2. Reproduction at the cellular level, mitosis and its biological role

Mitosis (from Greek mitos - thread), a type of cell division, as a result of which daughter cells receive genetic material identical to that contained in the mother cell. Karyokinesis, indirect cell division, is the most common method of cell reproduction (reproduction), which ensures the identical distribution of genetic material between daughter cells and the continuity of chromosomes in a number of cell generations.

Rice. 1. Scheme of mitosis: 1, 2 - prophase; 3 - prometaphase; 4 - metaphase; 5 - anaphase; 6 - early telophase; 7 - late telophase

The biological significance of mitosis is determined by the combination of the doubling of chromosomes in it by means of their longitudinal splitting and uniform distribution between daughter cells. The onset of mitosis is preceded by a period of preparation, including the accumulation of energy, the synthesis of deoxyribonucleic acid (DNA), and the reproduction of centrioles. The source of energy is rich in energy, or the so-called macroergic compounds. Mitosis is not accompanied by an increase in respiration, since oxidative processes occur in the interphase (the filling of the “energy reserve of the macaw”). Periodic filling and emptying of the energy reserve of the macaw is the basis of the energy of mitosis.

The stages of mitosis are as follows. Single process. Mitosis is usually divided into 4 stages: prophase, metaphase, anaphase, and telophase.

Rice. Fig. 2. Mitosis in the meristematic cells of the onion root (micrograph). Interphase

Rice. Fig. 3. Mitosis in the meristematic tufts of the onion root (micrograph). Prophase (loose tangle figure)

Rice. 4. Mitosis in the meristematic cells of the onion root (micrograph). Late prophase (destruction of the nuclear envelope)

METAPHASE - consists in the movement of CHROMOSOMES to the equatorial plane (metakinesis, or prometaphase), the formation of the equatorial PLATE ("mother star") and in the separation of chromatids, or sister chromosomes.

Rice. Fig. 5. Mitosis in the meristematic cells of the onion root (micrograph). prometaphase

Fig.6. Mitosis in the meristematic cells of the onion root (micrograph). metaphase

Rice. Fig. 7. Mitosis in the meristematic cells of the onion root (micrograph). Anaphase

Anaphase - the stage of divergence of chromosomes to the poles. Anaphase movement is associated with the elongation of the central filaments of VERETIN, which pushes the mitotic poles apart, and with the shortening of the chromosomal MICROTUBES of the mitotic apparatus. The elongation of the central filaments of the SPINDLE occurs either due to the POLARIZATION of "reserve macromolecules" that complete the construction of the MICROTUBES of the spindle, or due to the dehydration of this structure. The shortening of chromosomal microtubules is provided by the PROPERTIES of the contractile proteins of the mitotic apparatus, which are capable of contraction without thickening. TELOPHASE - consists in the reconstruction of daughter nuclei from chromosomes gathered at the poles, the division of the cell body (CYTOTHYMIA, CYTOKINESIS) and the final destruction of the mitotic apparatus with the FORMATION of an intermediate body. Reconstruction of daughter nuclei is associated with chromosome desperalization, RESTORATION of the nucleolus and nuclear envelope. Cytotomy is carried out by the formation of a cell PLATE (in plant cell) or by the formation of a fission furrow (in an animal cell).

Fig.8. Mitosis in the meristematic cells of the onion root (micrograph). Early telophase

Rice. Fig. 9. Mitosis in the meristematic cells of the onion root (micrograph). late telophase

The mechanism of cytotomy is associated either with the contraction of the gelatinized ring of the CYTOPLASMA encircling the EQUATOR (the “contractile ring” hypothesis) or with the expansion of the cell surface due to the straightening of the loop-like protein chains (the “MEMBRANE expansion” hypothesis)

Mitosis duration- depends on the size of the cells, their ploidy, the number of nuclei, as well as on environmental conditions, in particular on temperature. Mitosis lasts 30–60 minutes in animal cells, and 2–3 hours in plant cells. Longer stages of mitosis associated with the processes of synthesis (preprophase, prophase, telophase) self-movement of chromosomes (metakinesis, anaphase) is carried out quickly.

THE BIOLOGICAL SIGNIFICANCE OF MITOSIS - the constancy of the structure and the correct functioning of the organs and tissues of a multicellular organism would be impossible without the preservation of the same set of genetic material in countless cell generations. Mitosis provides important manifestations of vital activity: embryonic development, growth, restoration of organs and tissues after damage, maintenance of the structural integrity of tissues with constant loss of cells in the course of their functioning (replacement of dead erythrocytes, skin cells, intestinal epithelium, etc.) In protozoa, mitosis provides asexual reproduction.

3. Gametogenesis, characterization of germ cells, fertilization

Sex cells (gametes) - male spermatozoa and female eggs (or eggs) develop in the gonads. In the first case, the path of their development is called SPERMATOGENESIS (from the Greek sperm - seed and genesis - origin), in the second - OVOGENESIS (from Latin ovo - egg)

Gametes are sex cells, their participation in fertilization, the formation of a zygote (the first cell of a new organism). The result of fertilization is the doubling of the number of chromosomes, the restoration of their diploid set in the zygote. Features of gametes are a single, haploid set of chromosomes compared to the diploid set of chromosomes in body cells2. Stages of development of germ cells: 1) increase by mitosis in the number of primary germ cells with a diploid set of chromosomes, 2) growth of primary germ cells, 3) maturation of germ cells.

STAGES OF GAMETOGENESIS - in the process of development of sexual both spermatozoa and eggs, there are stages (fig.). The first stage is the period of reproduction, in which the primary germ cells divide by mitosis, as a result of which their number increases. During spermatogenesis, the reproduction of primary germ cells is very intense. It begins with the onset of puberty and proceeds throughout the entire reproductive period. Reproduction of female primary germ cells in lower vertebrates continues almost all life. In humans, these cells multiply with the greatest intensity only in the prenatal period of development. After the formation of the female sex glands - the ovaries, the primary germ cells stop dividing, most of of them dies and resolves, the rest remain dormant until puberty.

The second stage is the period of growth. In immature male gametes, this period is expressed unsharply. The sizes of male gametes increase slightly. On the contrary, future eggs - oocytes sometimes increase hundreds, thousands and even millions of times. In some animals, oocytes grow very quickly - within a few days or weeks, in others, growth continues for months and years. The growth of oocytes is carried out due to substances formed by other cells of the body.

The third stage is the period of maturation, or meiosis (Fig. 1).

Rice. 9. Scheme of the formation of germ cells

Cells entering the period of meiosis contain a diploid set of chromosomes and already double the amount of DNA (2n 4c).

In the process of sexual reproduction, organisms of any species from generation to generation retain their characteristic number of chromosomes. This is achieved by the fact that before the fusion of germ cells - fertilization - in the process of maturation, the number of chromosomes decreases (reduces) in them, i.e. from a diploid set (2n) a haploid set (n) is formed. The patterns of meiosis in male and female germ cells are essentially the same.

Bibliography

Gorelov A. A. Concepts of modern natural science. — M.: Center, 2008.


Dubnishcheva T.Ya. etc. Modern natural science. — M.: Marketing, 2009.


Lebedeva N.V., Drozdov N.N., Krivolutsky D.A. Biodiversity. M., 2004.


Mamontov S.G. Biology. M., 2007.


Yarygin V. Biology. M., 2006.


There are such levels of organization of living matter - levels of biological organization: molecular, cellular, tissue, organ, organism, population-species and ecosystem.

Molecular level of organization- this is the level of functioning of biological macromolecules - biopolymers: nucleic acids, proteins, polysaccharides, lipids, steroids. From this level, the most important life processes begin: metabolism, energy conversion, transfer hereditary information. This level is studied: biochemistry, molecular genetics, molecular biology, genetics, biophysics.

Cellular level- this is the level of cells (cells of bacteria, cyanobacteria, unicellular animals and algae, unicellular fungi, cells of multicellular organisms). A cell is a structural unit of the living, a functional unit, a unit of development. This level is studied by cytology, cytochemistry, cytogenetics, microbiology.

Tissue level of organization- This is the level at which the structure and functioning of tissues is studied. This level is studied by histology and histochemistry.

Organ level of organization- This is the level of organs of multicellular organisms. Anatomy, physiology, embryology study this level.

Organismal level of organization- this is the level of unicellular, colonial and multicellular organisms. The specificity of the organismic level lies in the fact that at this level the decoding and implementation of genetic information takes place, the formation of traits inherent in individuals of a given species. This level is studied by morphology (anatomy and embryology), physiology, genetics, paleontology.

Population-species level is the level of populations of individuals - populations and species. This level is studied by systematics, taxonomy, ecology, biogeography, population genetics. At this level, genetic and ecological features of populations, elementary evolutionary factors and their impact on the gene pool (microevolution), the problem of species conservation.

Ecosystem level of organization- this is the level of microecosystems, mesoecosystems, macroecosystems. At this level, types of nutrition are studied, types of relationships between organisms and populations in an ecosystem, population size, population dynamics, population density, ecosystem productivity, successions. This level studies ecology.

Allocate also biospheric level of organization living matter. The biosphere is a giant ecosystem that occupies part of the geographic envelope of the Earth. This is a mega ecosystem. In the biosphere, there is a cycle of substances and chemical elements, as well as the conversion of solar energy.

2. Fundamental properties of living matter

Metabolism (metabolism)

Metabolism (metabolism) is a set of chemical transformations occurring in living systems that ensure their vital activity, growth, reproduction, development, self-preservation, constant contact with the environment, the ability to adapt to it and its changes. In the process of metabolism, splitting and synthesis of molecules that make up cells occur; formation, destruction and renewal of cellular structures and intercellular substance. Metabolism is based on interrelated processes of assimilation (anabolism) and dissimilation (catabolism). Assimilation - the processes of synthesis of complex molecules from simple ones with the expenditure of energy stored during dissimilation (as well as the accumulation of energy during the deposition of synthesized substances in the reserve). Dissimilation - the processes of splitting (anaerobic or aerobic) of complex organic compounds, going with the release of energy necessary for the implementation of the vital activity of the organism. Unlike bodies of inanimate nature, exchange with the environment for living organisms is a condition for their existence. In this case, self-renewal occurs. Metabolic processes occurring inside the body are combined into metabolic cascades and cycles by chemical reactions, which are strictly ordered in time and space. The coordinated flow of a large number of reactions in a small volume is achieved by the ordered distribution of individual metabolic links in the cell (the principle of compartmentalization). Metabolic processes are regulated with the help of biocatalysts - special proteins-enzymes. Each enzyme has substrate specificity to catalyze the conversion of only one substrate. This specificity is based on a peculiar "recognition" of the substrate by the enzyme. Enzymatic catalysis differs from non-biological catalysis in extremely high efficiency, as a result of which the rate of the corresponding reaction increases by 1010 - 1013 times. Each enzyme molecule is capable of performing from several thousand to several million operations per minute without being destroyed in the process of participating in reactions. Another characteristic difference between enzymes and non-biological catalysts is that enzymes are able to accelerate reactions under normal conditions (atmospheric pressure, body temperature, etc.). All living organisms can be divided into two groups - autotrophs and heterotrophs, differing in energy sources and the necessary substances for their life. Autotrophs - organisms that synthesize from inorganic substances organic compounds using the energy of sunlight (photosynthetics - green plants, algae, some bacteria) or the energy obtained from the oxidation of an inorganic substrate (chemosynthetics - sulfur, iron bacteria and some others), Autotrophic organisms are able to synthesize all the components of the cell. The role of photosynthetic autotrophs in nature is decisive - being the primary producer of organic matter in the biosphere, they ensure the existence of all other organisms and the course of biogeochemical cycles in the circulation of substances on Earth. Heterotrophs (all animals, fungi, most bacteria, some chlorophyll-free plants) are organisms that need ready-made organic substances for their existence, which, acting as food, serve as both a source of energy and a necessary "building material". A characteristic feature of heterotrophs is the presence of amphibolism in them, i.e. the process of formation of small organic molecules (monomers) formed during the digestion of food (the process of degradation of complex substrates). Such molecules - monomers are used to assemble their own complex organic compounds.

Self-reproduction (reproduction)

The ability to reproduce (reproduce their own kind, self-reproduction) refers to one of the fundamental properties of living organisms. Reproduction is necessary in order to ensure the continuity of the existence of species, because. the lifespan of an individual organism is limited. Reproduction more than compensates for losses due to the natural extinction of individuals, and thus maintains the preservation of the species in a number of generations of individuals. In the process of evolution of living organisms, the evolution of methods of reproduction took place. Therefore, in the numerous and diverse species of living organisms that currently exist, we find different forms breeding. Many types of organisms combine several methods of reproduction. It is necessary to distinguish two fundamentally different types of reproduction of organisms - asexual (primary and more ancient type reproduction) and sex. In the process of asexual reproduction, a new individual is formed from one or a group of cells (in multicellular) of the mother organism. In all forms of asexual reproduction, the offspring have a genotype (set of genes) identical to the maternal one. Consequently, all the offspring of one maternal organism turns out to be genetically homogeneous and the daughter individuals have the same set of traits. In sexual reproduction, a new individual develops from a zygote formed by the fusion of two specialized germ cells (fertilization process) produced by two parental organisms. The nucleus in the zygote contains a hybrid set of chromosomes, which is formed as a result of the union of sets of chromosomes of fused gamete nuclei. In the nucleus of the zygote, thus, a new combination of hereditary inclinations (genes) is created, brought in equally by both parents. And the daughter organism developing from the zygote will have a new combination of features. In other words, during sexual reproduction, the implementation of a combinative form of hereditary variability of organisms occurs, which ensures the adaptation of species to changing environmental conditions and is an essential factor in evolution. This is a significant advantage of sexual reproduction over asexual reproduction. The ability of living organisms to self-reproduce is based on the unique property of nucleic acids to reproduce and the phenomenon of matrix synthesis, which underlies the formation of nucleic acid molecules and proteins. Self-reproduction at the molecular level determines both the implementation of metabolism in cells and the self-reproduction of the cells themselves. Cell division (self-reproduction of cells) underlies the individual development of multicellular organisms and the reproduction of all organisms. The reproduction of organisms ensures the self-reproduction of all species inhabiting the Earth, which in turn determines the existence of biogeocenoses and the biosphere.

Heredity and variability

Heredity provides material continuity (the flow of genetic information) between generations of organisms. It is closely related to reproduction at the molecular, subcellular and cellular levels. Genetic information that determines the diversity of hereditary traits is encrypted in the molecular structure of DNA (for some viruses, in RNA). The genes encode information about the structure of synthesized proteins, enzymatic and structural. The genetic code is a system of "recording" information about the sequence of amino acids in synthesized proteins using the sequence of nucleotides in the DNA molecule. The totality of all the genes of an organism is called the genotype, and the totality of traits is called the phenotype. The phenotype depends on both the genotype and factors of internal and external environment , which affect the activity of genes and determine regular processes. The storage and transmission of hereditary information is carried out in all organisms with the help of nucleic acids, the genetic code is the same for all living beings on Earth, i.e. it is universal. Due to heredity, traits are transmitted from generation to generation that ensure the adaptability of organisms to their environment. If during the reproduction of organisms only the continuity of existing signs and properties was manifested, then against the background of changing environmental conditions, the existence of organisms would be impossible, since a necessary condition for the life of organisms is their adaptability to environmental conditions. Variability is manifested in the diversity of organisms belonging to the same species. Variability can be realized in individual organisms in the course of their individual development or within a group of organisms in a series of generations during reproduction. There are two main forms of variability, which differ in the mechanisms of occurrence, the nature of the change in characteristics and, finally, their significance for the existence of living organisms - genotypic (hereditary) and modification (non-hereditary). Genotypic variability is associated with a change in the genotype and leads to a change in the phenotype. The basis of genotypic variability may be mutations (mutational variability) or new combinations of genes that occur during fertilization during sexual reproduction. In the mutational form, the changes are associated primarily with errors in the replication of nucleic acids. Thus, the emergence of new genes that carry new genetic information; new signs appear. And if the newly emerging signs are useful to the organism in specific conditions, then they are "caught up" and "fixed" by natural selection. Thus, the adaptability of organisms to environmental conditions, the diversity of organisms are based on hereditary (genotypic) variability, and the prerequisites for positive evolution are created. With non-hereditary (modification) variability, changes in the phenotype occur under the influence of environmental factors and are not associated with a change in the genotype. Modifications (changes in traits with modification variability) occur within the normal range of the reaction, which is under the control of the genotype. Modifications are not passed on to future generations. The value of modification variability lies in the fact that it ensures the adaptability of the organism to environmental factors during its life.

Individual development of organisms

All living organisms are characterized by the process of individual development - ontogenesis. Traditionally, ontogenesis is understood as the process of individual development of a multicellular organism (formed as a result of sexual reproduction) from the moment of formation of a zygote to the natural death of an individual. Due to the division of the zygote and subsequent generations of cells, a multicellular organism is formed, consisting of a huge number of different types of cells, various tissues and organs. The development of an organism is based on the "genetic program" (embodied in the genes of the chromosomes of the zygote) and is carried out in specific environmental conditions that significantly affect the process of implementing genetic information during the individual existence of an individual. On the early stages individual development, intensive growth occurs (increase in mass and size), due to the reproduction of molecules, cells and other structures, and differentiation, i.e. appearance of differences in structure and complication of functions. At all stages of ontogenesis, various environmental factors (temperature, gravity, pressure, food composition in terms of the content of chemical elements and vitamins, various physical and chemical agents) have a significant regulatory influence on the development of the organism. The study of the role of these factors in the process of individual development of animals and humans is of great practical importance, which increases with the intensification of anthropogenic impact on nature. In various fields of biology, medicine, veterinary medicine and other sciences, research is being widely carried out to study the processes of normal and pathological development of organisms, to elucidate the patterns of ontogenesis.

Irritability

An integral property of organisms and all living systems is irritability - the ability to perceive external or internal stimuli (impact) and respond adequately to them. In organisms, irritability is accompanied by a complex of changes, expressed in shifts in metabolism, electrical potential on cell membranes, physicochemical parameters in the cytoplasm of cells, in motor reactions, and highly organized animals are characterized by changes in their behavior.

4. Central dogma of molecular biology- a rule generalizing the implementation of genetic information observed in nature: information is transmitted from nucleic acids To squirrel but not in the opposite direction. The rule was formulated Francis Crick v 1958 year and brought into line with the data accumulated by that time in 1970 year. Transfer of genetic information from DNA To RNA and from RNA to squirrel is universal for all cellular organisms without exception; it underlies the biosynthesis of macromolecules. Genome replication corresponds to the DNA → DNA informational transition. In nature, there are also transitions RNA → RNA and RNA → DNA (for example, in some viruses), as well as a change conformations proteins transferred from molecule to molecule.

Universal ways of transferring biological information

In living organisms, there are three types of heterogeneous, that is, consisting of different polymer monomers - DNA, RNA and protein. The transfer of information between them can be carried out in 3 x 3 = 9 ways. The central dogma divides these 9 types of information transfer into three groups:

General - found in most living organisms;

Special - occurring as an exception, in viruses and at mobile elements of the genome or under biological conditions experiment;

Unknown - not found.

DNA replication (DNA → DNA)

DNA is the main way information is transmitted between generations of living organisms, so the exact duplication (replication) of DNA is very important. Replication is carried out by a complex of proteins that unwind chromatin, then a double helix. After that, DNA polymerase and its associated proteins build an identical copy on each of the two strands.

Transcription (DNA → RNA)

Transcription is a biological process, as a result of which the information contained in a DNA segment is copied onto a synthesized molecule. messenger RNA. Transcription is carried out transcription factors and RNA polymerase. V eukaryotic cell the primary transcript (pre-mRNA) is often edited. This process is called splicing.

Translation (RNA → protein)

Mature mRNA is read ribosomes during the translation process. V prokaryotic In cells, the process of transcription and translation is not spatially separated, and these processes are conjugated. V eukaryotic transcription site in cells cell nucleus separated from the broadcast site ( cytoplasm) nuclear membrane, so mRNA transported from the nucleus into the cytoplasm. mRNA is read by the ribosome in the form of three nucleotide"words". complexes initiation factors and elongation factors deliver aminoacylated transfer RNAs to the mRNA-ribosome complex.

5. reverse transcription is the process of forming a double-stranded DNA on a single-stranded matrix RNA. This process is called reverse transcription, since the transfer of genetic information in this case occurs in the “reverse” direction relative to transcription.

The idea of ​​reverse transcription was initially very unpopular, as it contradicted central dogma of molecular biology, which suggested that DNA transcribed to RNA and beyond broadcast into proteins. Found in retroviruses, For example, HIV and in case retrotransposons.

transduction(from lat. transductio- movement) - transfer process bacterial DNA from one cell to another bacteriophage. General transduction is used in bacterial genetics to genome mapping and design strains. Both temperate and virulent phages are capable of transduction, the latter, however, destroy the bacterial population, so transduction with their help does not have of great importance either in nature or in research.

A vector DNA molecule is a DNA molecule that acts as a carrier. The carrier molecule must have a number of features:

Ability to autonomously replicate in a host cell (usually bacterial or yeast)

The presence of a selectable marker

Availability of convenient restriction sites

The most common vectors are bacterial plasmids.

LEVELS OF LIFE ORGANIZATION

Nature is a holistic, but heterogeneous system, which is characterized by hierarchical organization. Under system, in science they understand unity, or integrity, composed of many elements that are in regular relationships and connections with each other. The main biological categories, such as the genome (genotype), cell, organism, population, biogeocenosis, biosphere, are systems. Hierarchical called a system in which parts, or elements, are arranged in order from lowest to highest. So, in wildlife, the biosphere is composed of biogeocenoses represented by populations of organisms of different species, and the bodies of organisms have a cellular structure.

The hierarchical principle of organization makes it possible to single out individual levels, which is convenient from the point of view of studying life as a complex natural phenomenon.

Widely used in biomedical science level classification in accordance with the most important parts, structures and components of the body, which are direct objects of study for researchers of various specialties. Such objects can be an organism as such, organs, tissues, cells, intracellular structures, molecules. The selection of the levels of the classification under consideration is in good agreement with the resolution of the methods used by biologists and doctors: studying an object with the naked eye, using a magnifying glass, a light-optical microscope, electron microscope, modern physico-chemical methods. The relationship between these levels and the typical sizes of the studied biological objects is also obvious (Table 1.1).

Table 1.1. The level of organization (study) allocated in a multicellular organism (according to E. Ds. Roberts et al., 1967, with changes)

The interpenetration of ideas and methods of various fields of natural science (physics, chemistry, biology), the emergence of sciences at the junction of these fields (biophysics, biochemistry, molecular biology) led to an expansion of the classification, up to the allocation of molecular and electron-atomic levels. Medico-biological research carried out at these levels is already providing practical access to public health. Thus, devices based on the phenomena of electron paramagnetic and nuclear magnetic resonance are successfully used to diagnose diseases and conditions of the body.

The ability to explore the fundamental biological processes that take place in the body at the cellular, subcellular and even molecular levels is outstanding, but not the only one. hallmark modern biology. It is characterized by an in-depth interest in the processes in the communities of organisms that determine the planetary role of life.

Thus, the classification was replenished with supraorganismal levels, such as species, biogeocenotic, biospheric.

The above classification is followed by most of the specific biomedical and anthropobiological sciences. This is not surprising, since it reflects the levels of organization of living nature through the historically established levels of its study. The objective of a medical school biology course is to teach the most complete description biological "inheritance" of people. To solve this problem, it is advisable to use a classification that most closely reflects precisely levels of life organization.

In the named classification, molecular-genetic, cellular, organismic, or ontogenetic, population-species, biogeocenotic levels are distinguished. The peculiarity of this classification lies in the fact that the individual levels of the hierarchical system of life are determined in it on a common basis of allocation for each level. elementary unit and elementary phenomenon. An elementary unit is a structure or an object, the regular changes of which, designated as an elementary phenomenon, make a contribution specific to the corresponding level to the process of preserving and developing life. The correspondence of the distinguished levels to the key moments of the evolutionary process, outside of which no living creature stands, makes them universal, extending to the entire area of ​​life, including man.

The elementary unit on molecular genetic level a gene is a fragment of a nucleic acid molecule, in which a qualitatively and quantitatively determined amount of biological (genetic) information is recorded. The elementary phenomenon consists primarily in the process convariant reduplication, or self-reproduction, with the possibility of some changes in the content of the information encoded in the gene. By means of DNA replication, the biological information contained in the genes is copied, which ensures the continuity and preservation (conservatism) of the properties of organisms in a number of generations. Reduplication is thus the basis of heredity.

Due to the limited stability of molecules or synthesis errors in DNA (from time to time, but inevitably), disturbances occur that change the information of genes. In subsequent DNA replication, these changes are reproduced in copy molecules and are inherited by organisms of the daughter generation. These changes occur and replicate naturally, which makes DNA replication covariant, i.e. occurring sometimes with some modifications. These changes in genetics are called genetic(or true) mutations. Replication convariance thus serves as the basis for mutational variation.

Biological information contained in DNA molecules is not directly involved in life processes. It passes into an active form, being transferred to protein molecules. Marked transfer is carried out due to the mechanism matrix synthesis, in which the original DNA serves, as in the case of reduplication, as a template (form), but for the formation of not a daughter DNA molecule, but a messenger RNA that controls protein biosynthesis. The noted gives grounds to classify the matrix synthesis of informational macromolecules as an elementary phenomenon at the molecular genetic level of life organization.





The embodiment of biological information in specific life processes requires special structures, energy and various chemical substances(substrates). The conditions described above in wildlife are provided by the cell, which serves as an elementary structure cellular level. An elementary phenomenon is represented cellular metabolic reactions forming the basis of the flows of energy, substances and information. Thanks to the activity of the cell, substances coming from outside are converted into substrates and energy, which are used (in accordance with the existing genetic information) in the process of biosynthesis of proteins and other compounds needed by the body. Thus, at the cellular level, the mechanisms of transmission of biological information and the transformation of substances and energy are conjugated. An elementary phenomenon at this level serves as the energy and material basis of life at all other levels of its organization.

elementary unit body / that level is an individual in its development from the moment of origin to the termination of existence as a living system, which also allows us to call this level ontogenetic. Regular changes in the body individual development constitute an elementary phenomenon of this level. These changes ensure the growth of the organism, the differentiation of its parts and, at the same time, the integration of development into a single whole, the specialization of cells, organs and tissues. In the course of ontogenesis, under certain environmental conditions, hereditary information is embodied in biological structures and processes, and the phenotype of organisms of a given species is formed on the basis of the genotype.

elementary unit population-species level serves population - a group of individuals of the same species. The association of individuals into a population occurs due to the commonality gene pool, used in the process of sexual reproduction to create the genotypes of individuals of the next generation. The population, due to the possibility of interpopulation crossings, is open genetic system. The effect on the gene pool of a population of elementary evolutionary factors, such as the mutation process, fluctuations in the number of individuals, natural selection, leads to evolutionary significant changes gene pool that represent elementary phenomena at a given level.

Organisms of one species inhabit a territory with known abiotic parameters (climate, soil chemistry, hydrological conditions) and interact with organisms of other species. In the process of joint historical development in a certain territory of organisms of different systematic groups, dynamic, time-stable communities are formed - biogeocenoses, which serve as the basic unit biogeocenotic(ecosystem) level. An elementary phenomenon at the considered level is represented by energy flows and cycles of matter. The leading role in these cycles and flows belongs to living organisms. Biogeocenosis is a system open in material and energy terms. Biogeocenoses, differing in species composition and characteristics of their abiotic part, are united on the planet into a single complex - the area of ​​​​distribution of life, or biosphere.

The above levels reflect the most important biological phenomena, without which evolution and, consequently, the very existence of life are impossible. Although the elementary units and phenomena at the distinguished levels are different, they are all closely interconnected, solving their specific task within the framework of a single evolutionary process. The elementary foundations of this process are associated with convariant reduplication at the molecular genetic level in the form of the phenomena of heredity and true mutational variability. Special Role cellular level consists in energy, material and information support happening at all other levels. At the ontogenetic level, the biological information contained in the genes is transformed into a complex of signs and properties of the organism. The resulting phenotype becomes available to the action of natural selection. At the population-species level, the evolutionary value of changes related to the molecular-genetic, cellular and ontogenetic levels is determined. The specific role of the biogeocenotic level consists in the formation of communities of organisms of different species adapted to living together in a certain habitat. An important distinguishing feature of such communities is their stability over time.

The considered levels reflect overall structure evolutionary process, the natural result of which is man. Therefore, the elementary structures and phenomena typical of these levels also apply to people, however, with some peculiarities due to their social nature.