Who introduced a term gene into science. The gene is a medical encyclopedia. Changes in chromosomes during cell division

The concept of "gene" arose long before the occurrence of science, he studied. Czech naturalist, founder of modern genetics, Grgen Mendel In 1865, analyzing experiments on the crossing of pea, came to the conclusion that the inheritance of signs is carried out by discrete particles, which he called "recesses" or hereditary "factors". In 1868, Charles Darwin proposed a "temporary hypothesis" paranise, according to which all cells of the body separate special particles, or gemmos, and of them, in turn, sex cells are formed.

Then Gogo de Fris in 1889, 20 years after Ch. Darwin, put forward his hypothesis of intracellular paraken and introduced the term "Pangen" to indicate the material particles available in cells that are responsible for quite specific individual hereditary properties characteristic of this species. Ghemulas C. Darwin represented fabrics and organs, de freeza Pangens corresponded to hereditary features inside the species.

In 1906, the English scientist W. Betson introduced the name of science - "Genetics", and three years later, in 1909, the Danish scientist V. Johansen found it convenient to use only the second part of the term Gogo de Freeza "gene" and replace them indefinite The concept of "primitive", "determinant", "hereditary factor". At the same time, V. Johansen emphasized that "this term is completely not connected with any hypotheses and has the advantage due to its shortness and ease with which it can be combined with other notation." He immediately formed a key derivative concept of "genotype" to designate the hereditary constitution of the Games and the zygota in contrast to the phenotype. Thus, the concept of gene as an elementary unit of heredity was included in the genetics. In the future, it was constantly specified thanks to numerous discoveries: the localization of genes in chromosomes was proved; It turned out that the genes change as a result of mutations; The concept of alleles and their localization in the appropriate chromosome homologous chromosomes was developed. In all genetic studies, the gene becomes a generally accepted unit of heredity.

Among the genetics was universal conviction in the indivisibility of the gene. They imagined the gene as a whole as the last elementary unit of heredity. But at the beginning of the 1930s, the doubt was that the gene is indivisible. The first signal in this respect laid the opening of multiple alleles, or a series of multiple alleles. It turned out that the single gene may change, giving a number of mutations associated with changes in a certain feature.

In some organisms, and above all, Drosophila has been opened by a series of multiple alleles containing dozens of various mutations, and a series of alleles has been discovered in horned livestock, including up to 80 mutations, i.e., as a result of mutations, 80 different states of one locus arose.

Since the beginning of the 1930s, a new stage began in the study of the gene. The development of its structure was occupied by the laboratory A. S. Sererovsky. Work A. S. Sererovsky, then N. P. Dubinina showed that the gene has a much more complex structure than expected earlier.

Works were conducted on the study of the SCUTE gene, localized in the sex chromosome of Drosophila. This gene determines the development of bristles on the body of flies. Different allel mutations of the gene concerned the underdevelopment of the bristles on certain particular areas of the bodies of drosophila and varying degrees of the reduction of bristles. With a genetic analysis of these mutations, crossing them with each other it turned out that in the heterosigote they behave partly as allel genes, and partly as mutations of independent locus chromosomes. Thus, the gene turned out to be a complex system in which mutations lead to a change of only individual parts.

The name "Multiple Alleles" was replaced by more successful "stepped alleles" and was formulated by a hypothesis about the complex structure of the gene. The gene as a whole is called "Basigen", and mutating alleles "Transgenami".

The further development of the teaching on the structure of the gene is associated with the transition of methods of genetic studies with chromosomal to the molecular level. It was important to use in the works of genetics until little of the microorganisms studied: bacteria and even non-cell forms - viruses. Especially important in these works were the study of bacteriophages from the group "T" infecting an intestinal wand.

In the study of the nature of the gene, Benzer and a number of other researchers conducted on bacteriophages and other objects had especially importance. As a result of his works, Benzer introduced three new concepts:

1. It was previously believed that the crossingler could occur only between the genes and, thus, the gene is an elementary unit of genetic recombination. However, it is proved that recombination occurs within the gene. The smallest unit of recombination is called a reconna.
2. Previously considered the gene unit of mutation. However, it was found that changes in individual sections inside the complex gene lead to a change in its function. The smallest unit capable of change was called Muton.
3. The gene was considered a function of the function. Numerous studies have shown that the function of the gene may vary depending on whether two mutant allele of the complex gene in one chromosome is located, and their normal alleles in the homologous (cis-position), or mutant alleles are located in two homologous chromosomes (linked). The unit function is proposed to call a cystron.

The parallel work of biochemists and genetics showed that the smallest value of the reconight and the muton is close to the magnitude of one or more nucleotides. Cystron is homologous to the DNA section, the "encoding" synthesis of a certain polypeptide, and contains a thousand and more nucleotides.

Functional genetic classification of genes

There are several classifications of genes (allelic and non-allele, lethal and semi-liter genes, etc.). The characteristics of the gene as a unit of the function of the hereditary material and the system principle of the organization of the genotype are reflected in the functional genetic classification of hereditary deposits

Structural They are called genes controlling the development of specific signs. The product of primary activity of the gene is either IRNNA and further polypeptide or RRNA and TRNA. Thus, structural genes contain information about the amino acid or nucleotide sequences of macromolecules. The structural genes of the three subgroups given in the classification are distinguished by the degree of playiotropic action, and pronounced playotropia distinguishes the genes of the second and third subgroups that are actively functioning in all cells. With their mutations, various and extensive violations of the body's development are observed. It is no coincidence that therefore, these genes are presented in the genotype in the amount of several dozen copies and are formed by the average-reserving DNA sequences.

Menage modulators shift in one direction or another process of development of a feature or other genetic phenomena, for example mutation frequency structural genes. Some structural genes simultaneously performs the role of modulators (see an example of the "position effect"). Other modulator genes seem to be deprived of any other genetic functions. The emergence of such genes in evolution was of great importance. Thanks to the playiotropic action, many structural genes, along with favorable and necessary for the normal development of the organism, have undesirable effects that reduce the viability of individuals. An unfavorable effect is weakened by modulator genes.

To regulatory The genes coordinating the activity of structural genes, which control the time of incorporating various loci in the process of individual development, depending on the type of cells of the multicellular organism, as well as from the state of the medium.

Molecular biological ideas about the structure and functioning of genes

The ideas of molecular biology have now been penetrated into all branches of life science and identified the main trends in the development of theoretical, experimental and applied biology. Molecular biology developed in the course of studies of the physicochemical properties and biological role of nucleic acids and proteins. Its the foundations were laid by works on the genetics of viruses and phages, the chemical nature of the hereditary material, the mechanism of protein biosynthesis, biological code, the patterns of the ultrastructural organization of the cell. In this regard, the molecular biology can be determined as a region of studying the patterns of the structure and changes in information macromolecules and their participation in the fundamental processes of vital activity.

In the field of genetics, molecular biology revealed the chemical nature of the substance of heredity, showed physicochemical prerequisites for storage in the information cell and accurate copying it for transmission in a number of generations. DNA of most biological objects (from mammals to bacteriophage) contains equal amounts of nucleotides with purine (adenine, guanine) and pyrimidine (thymine, cytosin) nitrogenous bases. This means that the combination of DNA molecules into the double helix is \u200b\u200bcarried out naturally, in accordance with the principle of complementarity - adenyl nucleotide is associated with a thymidyl nucleotide, and a guanilla with citidyl (Fig. 53). This design makes it possible a half-party DNA reduction method. At the same time, the DNA pair of A - T and Mr. DNA are collected randomly - a + t ≠ r + C. Consequently, by independent combination of nucleotides, differing in a nitrogenous base, on the length of DNA molecules, it is possible to record a variety of information, the volume of which is proportional to The amount of nucleic acid in the cell.

According to the molecular biological representation of the gene, as a unit of functioning of hereditary material is characterized by a complex structure. Many details of the fine structure of the gene remain unknown. At the same time, the successes of modern science in this area are large enough to draw a fundamental model of a functioning gene.

The functional activity of the gene consists in the synthesis on the DNA molecule of RNA molecules or transcription (rewriting) of biological information in order to use it for the formation of protein. Transcription units (transcriptones) are exceeded in size structural genes (Fig. 54). According to one of the TrancoPton models in eukaryotes, it consists of non-informative (acceptor) and informative zone. The latter is formed by structural genes (cystones), which are separated by DNA inserts - spacers that do not carry information about the amino acid sequences of proteins. The non-informative zone begins the genomoter gene (P), to which the RNA polymerase enzyme is joined, catalyzing the reaction of the DNA dependent formation of ribonucleic acids. Next follows acceptor genes or genes-operators (α 1, α 2, etc.), connecting regulatory proteins (R 1, R 2, etc.), the changes of which "open" DNA of structural genes (S 1, S 2 etc.) for reading information. One large RNA molecule is synthesized on the transcripton. Thanks to processing, the non-informative part is destroyed, and the informative is split into fragments corresponding to individual structural genes. These fragments in the form of IRNK for the synthesis of specific polypeptides are transported to the cytoplasm. According to the model in the transcript, several structural genes are located. A group of these genes forms a functional block and is called operon. The functional unity of operences depends on the presence of genes generators, which perceive signals from the metabolic apparatus of the cytoplasm and activate structural genes.

The nature of signals governing the function of genes has been studied in prokaryotes. These are proteins whose synthesis is controlled by special regulatory genes acting on gene generators. The activation of structural genes by means of gean-regulators and operators is presented in the diagram (Fig. 55). Under normal conditions, the regulator gene is active and the synthesis of protein-repressor proceeds in the cell, which is associated with the operator gene and blocks it. It turns off the entire opera from the function.

Opero inclusion occurs if the substrate molecules are penetrated into the cytoplasm, to digest which the synthesis of the corresponding enzyme is renewed. The substrate joins the repressor and deprivates its ability to block the generator generator. In this case, information from the structural gene is read and the desired enzyme is formed. In the described example, the substrate plays the role of the inducer (patron) of the synthesis of "his" enzyme. The latter launches the biochemical reaction in which this substrate is used. As its concentration decreases, the repressor molecules are released, which block the activity of the generator generator, which leads to the turning off of the operon. The bacteria describes the regulation system by translating the active structural genes into an inactive state depending on the concentration in the cytoplasm of the final product of a certain biochemical reaction (Fig. 56). At the same time, the genetic control of the genet regulator forms an inactive form of the gene-operator's repressor. The repressor is activated as a result of interaction with the final product of this biochemical reaction and, blocking the generator generator, turns off the corresponding opera. The synthesis of the enzyme catalyzing the formation of a substance activating the repressor stops. The described regulatory systems of structural genes are adaptive. In the first example, the synthesis of the enzyme is started by entering the substrate cage of the appropriate reaction, in the second - the formation of the enzyme stops as soon as the need disappears in the synthesis of a certain substance.

The principles of regulation of genetic activity in eukaryota, apparently, are similar to those of bacteria. At the same time, the appearance of a nuclear shell, the complication of gene interactions in the conditions of diploidity, the need for a thin correlation of the genetic functions of individual cells of the multicellular organism has led to the transition to the eukaryotic type of cell organization the complication of regulatory genetic mechanisms, genetically biochemical and cyber bases of which are in many respects clarified. It can also be assumed that the number of generator gene operators has increased in evolution. The transcription inductors of many structural genes eukaryot are hormones. It is assumed to have integrators genes, including in response to an incentive at the same time "Battery of Gene". The genetic system of higher organisms is different, apparently big flexibility reactions to the effect of non-mental factors. In confirmation of this assumption, consider a number of factors. Thus, some of the structural genes of animals are not continuous sequences of codons, and are composed of fragments that are interrupted by non-informative DNA sections. The hemoglobin of the r-polypeptide of the hemoglobin, for example, is interrupted by an insert from 550 nucleotides pairs. The plot corresponding to this insert is absent in the mature globin IRNK, which indicates its destruction during the processing of primary transcribed RNA with the reunification of IRNK informational fragments. The information plots of such genes received the name of exons, "silent" - intron, and the reunification process of IRNK - splaxing information fragments (fusion). The amount of DNA in nitrons is 5-10 times higher than in the exon field. It is assumed that splicing serves as a mechanism for the formation of some genes at the time of their functional activity, i.e., at the level of IRNA.

Known also "wandering" structural genes, the position of which in the chromosome changes depending on the phase of the life cycle. Thus, the "heavy" and "light" immunoglobulin polypeptides consist of constant (C) and variable (y) sites, the synthesis of which is controlled by adhesive, but different genes. In mature plasma cells, these genes are separated by a non-trans-crossed insert in a length of 1000 pairs of nucleotides. In the cells of embryos called insert many times longer. Thus, in the process of cell differentiation, the liabilities of genes change. The study of the mechanisms for regulating the genetic activity and gene interactions in eukaryota represents the most important area of \u200b\u200bmodern molecular biology and genetics.

Gena properties

The gene as a unit of functioning of hereditary material has a number of properties.

1. Specificness is a unique sequence of nucleotides for each structural gene, i.e. Each gene encodes its sign;
2. Integrity - as a functional unit (programming of protein synthesis) gene by indivisible;
3. Discreteness - As part of the gene, there are subunits: Muton - subunit that is responsible for mutation, reconnaissance - is responsible for recombination. The minimum value is a pair of nucleotides;
4. Stability is gene, as a discrete unit of heredity is characterized by stability (constant) - in the absence of mutation, it is transmitted in a number of generations unchanged. The frequency of spontaneous mutation of one gene is approximately 1 · 10 -5 per generation.
5. Lability - the stability of genes is not absolute, they may change, mutate;
6. Pleotropia is a multiple effect of a single gene (one gene is responsible for several signs);

   An example of the playiotropic effect of a man in a person serves Martan syndrome. Although this hereditary disease depends on the presence of one modified gene in the genotype, it is characterized in typical cases of triad signs: the sliding of the lens of the eye, the aneurysm of the aorta, changes in the musculoskeletal system in the form of "spider fingers", deformed chest, High Stop Arch. All listed features are complex. Apparently, they are based on the same defect for the development of connective tissue.

   Since the product of the gene function is most often a protein-enzyme, the severity of the playiotropic effect depends on the prevalence of the biochemical reaction body, which catalyzes the enzyme synthesized under the genetic control of this gene. The prevalence of lesions in the body in the case of a hereditary disease is the greater than the pronounced playiotropic effect of the changed gene.

The gene, which is available in the genotype in the amount required for the manifestation (1 allele for dominant signs and 2 alleles for recessive), can manifest itself in the form of a sign in different extent in different organisms (expressiveness) or not to manifest themselves (penetrant). Expressiveness and penetrantity are determined by the factors of the medium (exposure to environmental conditions - modification variability) and the influence of other genes of the genotype (combinative variability).

1. Expressiveness is the severity of the gene in the sign or the degree of phenotypic manifestation of the gene.

   For example, the alleles of blood groups AV0 in humans have permanent expressivity (always manifest themselves 100%), and alleles that determine the color of the eye are changeable expressiveness. Recessive mutation that reduces the number of facets of the eye in Drosophila, in different individuals in different ways reduces the number of facets up to their complete absence.

2. Penetrant - the frequency of the phenotypic manifestation of the feature in the presence of an appropriate gene (ratio (as a percentage) of the number of individuals with this feature, to the number of individuals having this gene);

   For example, the penetrant of congenital dislocation of the thigh in a person is 25%, i.e. Disease suffers only 1/4 recessive homozygotes. The medical and genetic meaning of penetrantiness: a healthy person who has one of the parents suffers from an incomplete penetrantity, may have an unprinted mutant gene and transfer it to children.

- RNA), defining (encoding) the possibility of developing any feature. The gene is a functionally indivisible unit, i.e. one gene, as a rule, is responsible for one elementary sign. Such a sign of a molecular level can be a protein or RNA molecule, and at the body level, for example, the color or color of the human eye. At the same time, the possibility of implementing the gene, its manifestations in the form of a sign depend on a number of factors, primarily on the interaction with other genes forming the medium (see genotype).

Studying the structure, organization, principles of generation of genes (or somewhat wider - genetic material) - the central problem of genetics at all stages of its development. At the same time, the representations of the gene as a hereditary factor, which has a function, physical nature, the ability to variability and other properties, was significantly changed and complemented. In 1865, Mendel, on the basis of its plants, proved the existence of discrete hereditary "deposits", which Danish geneticist V. Johansen in 1909 called genes. Mendel's work discovered the possibility of accurate genetic () analysis of heredity and after their repetition in 1900 gave an impetus to the unusually rapid formation of genetics. Already in the first third of the 20th century. It was found that the genes are linearly located in the chromosomes of the cell nucleus (see the chromosomal theory of heredity) that they may be subject to natural or caused artificially inherited changes - mutations and that when passing them from parents to descendants, their redistribution occurs - recombination. In this case, it turned out that the gene as a unit of function and gene as a unit of mutation and recombination is not the same. This was the idea of \u200b\u200bthe complex structure of the gene, but the question of its chemical nature remained unresolved. Finally, in the 40s. On microorganisms it was shown that the genes of genes are deoxyribonucleic acid (DNA), and in 1953 its spatial model was created (etc. Double spiral), which explained the biological functions of this gigantic molecule. Stormy development of the molecular biology of gene began. Soon, the methods of recording genetic information (genetic code) and its transmission mechanism in replication, transcription and broadcast processes were disclosed. Back in the 40s. The concept was put forward: "One gene is one enzyme", according to which each gene defines the structure of any enzyme (protein). Now this provision was specified: if the protein consists of several polypeptide chains, each of them is encoded by a separate genome, i.e., more correctly, the formula: "One gene is one polypeptide chain". In cells there are a set of genes specific to organisms of one biological species, and mechanisms for regulating their activity. Due to this, there is an adjustable synthesis of enzymes and other proteins, providing specialization of cells and tissues in the process of developing the body from fertilized egg and supporting the type of metabolism characteristic.

In the future, the peculiarities of the organization of genetic material in prokaryotic, eukaryotes and viruses were investigated, as well as in cellular organoids - mitochondria and chloroplasts, opened by T. N. Mobile genes moving by software are decrypted the structure (nucleotide sequence) of genomes of a number of organisms, including a person. The development of methods for isolating, cloning and hybridization of individual genes (DNA sections) led to the emergence of an important genetic engineering, a number of directions in biotechnology. See also allele, genome, chromatin.

Discrete unit heredity The highest organisms are gene. The combination of all genes of a certain biological species is determined by the term genome (sometimes this term refers to the total genetic system of a separate cell or a particular body). The gene in its most practical understanding is a strictly defined part of the DNA molecule, the sequence of which contains all the information necessary for the synthesis of the protein or RNA molecule. Genetic information is encrypted by universal for all living organisms of the genetic code, which is a set of nucleotide triplets - codons. Each such triplet (that is, each sequence of 3 nucleotides) encodes the synthesis of one, strictly defined amino acid as part of the protein.

Reading Codon B. process Genetic information transmissions occurs sequentially (the principle of the linearity of the genetic code), and any nucleotide may be part of only one codon (the principle of non-redeebles of the genetic code). The genetic code is degenerate, i.e. It allows for the encoding of each of 20 amino acids in several trucks of triplets (all such combinations can be 64). Deciphering the exact sequence of nucleotides of a certain information section of the gene allows one to unambiguously identify the sequence of amino acids in the corresponding polypeptide segment of the protein and its size. A complete haploid human genome (i.e., the DNA encoded by one semantic thread) includes, approximately, about 30,000-40,000 genes.

Human genes and other higher organisms They have an extremely complex structural and functional organization and contain various nucleotide sections in their biological role. Some of them (exons) are relatively short, represent coding sequences and determine the amino acid composition of proteins; Other portions of gene (intron) are usually significantly longer and not carried by direct information load. The final role of the intronons has not yet been established; It is assumed that they may be related to the regulation of gene expression and the control of the subtle mechanisms of "reading" of genetic information. The genes also include special regularity areas (promoters, enhancers, various signal sequences), ensuring initiation, intensity and a certain temporal sequence of nucleotide synthesis processes on a DNA matrix, as well as a modification of intermediate polynucleotide products.
By indicative estimatedThe actual coding sequences of DNA are not more than 3-10% of the entire human genome.

In any cell organism It contains a complete set of genes, but only a small part is functionally active in each specific tissue, i.e. Expressed. The expression of the gene understands the implementation of the genetic information recorded in it, leading to the synthesis of primary molecular products of the gene - RNA and protein. It is the temporary and tissue selectivity of gene expression that determines the specifics of differentiation and functioning of various organs, tissues and cell cells in ontogenesis.

Gene I. (Greek. Genos, Origin)

the structural and functional unit of genetic material, a hereditary factor, which can be conventionally represented as a molecule segment (in some viruses - molecules), including a nucleotide sequence in which the primary structure of the polypeptide (protein) is encoded or the transport or ribosomal RNA molecule, which is controlled by this. Determining the primary structure of a particular protein, the gene thus determines the formation of a separate feature of the body or cell.

The assumption of the existence of hereditary factors was first expressed by Mendel (G.J. Mendel) in 1865, which came to the conclusion that the transfer of a sign of parents to the offspring is due to the transmission through these hereditary factors, each of which is transmitted as something as an integer and independent. In 1909, Johannsen (W. Johannsen) proposed to denote Mendelian hereditary factors by the term "genes". In 1911, Morgana (TH.N. Morgan) and its employees were shown that the gene is a plot and that separate consists of genes that are consistently located at its length (see chromosome) . Each gene occupies a certain place () on the chromosome. Later Morgan and his employees were created the first chromosomal maps on which they showed the location of individual genes on chromosomes. The combination of chromosomal (or nuclear) genes constituting the so-called genome and genes localized in cytoplasmic structures - mitochondria, plastids, plasmids, determines cells or organism.

The gene can directly determine the presence of any sign (hair dryer) of the body or to participate in the formation of several signs (phenomenon of playiotropy). However, the bulk of the person in humans is formed as a result of the interaction of many genes (phenomenon of the polygenation). The loss of the gene or its change (see Mutagenez) leads to a change in the characteristic controlled by this genome. The degree of manifestation of a feature controlled by a particular genome (gene) also depends on environmental conditions. At the same time, even within a relative group of individuals, which in similar conditions of existence, the manifestation of the same gene may vary according to the degree of severity. All this suggests that in the formation of signs, the genotype acts as a holistic, functioning in strict dependence on intorganism and the environment. So, a separate feature or a set of all signs of the body, i.e. It is the result of the interaction of the genotype with environmental; The ability of the gene phenotypically to manifest itself in one way or another is called a gene penetrant.

In diploid organisms, i.e. In organisms whose somatic cells have, genes are presented by a pair of alleles. Allel is one of the possible states or one of possible options gene; Theoretically, the number of alleles of each gene is innumerable, but not all of them passed evolutionary. In homologous chromosomes, allele genes are located in homologous loci. Allel genes can be composed of identical (phenomenon of homozygosity) or various (phenomenon of heterozygency) alleles. In heterozygotes (organisms whose allelic genes are different) the manifestation of one allele at the level of the characteristic of the body (phenotypic manifestation) can completely suppress the manifestation of another allele. The overwhelming allele is called dominant, and the repressed is recessive. Accordingly, the signs controlled by them are called dominant or recessive. The phenotypic manifestation of recessive genes can be observed only in those organisms that are homozygous in relation to such a recessive gene, i.e. Both allele genes are recessive in them, or in the case when the gene does not have an allelic pair, for example, some genes located on one of the genital chromosomes at their XY-combination. Heterozygous organisms have a joint (codominant) manifestation of alleles. Thus, the concepts "" and "recessive" reflect the contribution of this gene into the formation of a specific feature. The property of the gene to suppress or be depressed largely depends on the gene environment - the genotypic medium in which this gene is located. Transferring a gene to another place of chromosome, entering the change in its gene environment, leads to the loss of this genome of its properties, incl. Even such a property developed in the process of long-term evolution as the ability to dominate. This phenomenon is called the genet position effect. When the gene is returned to the previous position on the chromosome, its ability to dominate is restored.

Studying the mechanisms for regulation of the function of the gene, French Genetics Jacob (F. Jacob) and (J.L. Monod) concluded that there are structural and regulatory genes. The structural genes include genes that control (encoded) the primary structure of matrix, or informational, RNA, and through them the sequence of amino acids in the synthesized polypeptides (see proteins) . Another group of structural genes is genes that determine the sequence of nucleotides in polynucleotide rivoscopic RNA circuits and transport RNA (see nucleic acids) .

Regulatory genes control the synthesis of specific substances, the so-called DNA-binding proteins that regulate structural genes.

Using the ability of some bacteriophages to transfer fragments of the bacterial chromosome into other bacterial cells (transduction phenomenon), Becvit (J.R. Beckwith) and its staff in 1969 were first allocated, accurately determined the size of the individual genet of the intestinal wand and received its electron diffraction pattern. In 1967-1970 Korana (N.G. Khorana) carried out the chemical synthesis of an individual gene.

As the possibilities of genetic analysis increase (see Genetics), all new evidence was obtained that the gene, being a functional unit, at the same time it has a very complex structure. The first evidence of the complexity of the organization of the gene was received in 1929. Soviet scientists A.S. Silver, N.P. Dubinin and I.I. Agola

Along with the structural and regulatory genes in DNA molecules, areas of repeating nucleotide sequences were found, whose functions are not known, as well as migrating nucleotide sequences - the so-called mobile genes. Pseudogens are also found, which are inactive copies of known genes, but located in other parts of the genome.

In 1953 english Biochemist Creek (F. N.S. CRICK) and American Biochemist Watson (JD Watson) offered the buildings of the DNA molecule and suggested, soon fully confirmed that the sequence of nucleotides in the DNA polynucleotide chain is the code, in accordance with which the amino acid residue is connected. In the polypeptide chain of protein molecules under the control of the respective genes. In the future, this genetic was studied in more detail. It was found that the inclusion of a single amino acid residue into the polypeptide chain under construction was determined by the combination of three successively arranged nucleotides, the so-called triplets, and the inclusion of one and the same can encode several different triplets is proved that the genetic code is universal, i.e. It is one for all living organisms. The implementation of information, "recorded" in the gene, is carried out with the help of an intermediary, which is one of the types of RNA - matrix, or information, RNA (). MRNA occurs on the DNA molecule as on the matrix. Such a matrix synthesis ensures the accuracy of "rewriting" (transcription) features of the nucleotide gene sequence on the MRNA molecule. Synthesized mRNA from the cell nucleus enters the cytoplasm, where on ribosomes (cm. Cell), genetic information is implemented (the transmission process), which is embodied in the sequence of amino acids connected to the protein polypeptide chain.

The average protein molecule sizes contains about 300 amino acid residues. Consequently, the average gene must contain at least 1000-1500 nucleotides. However, the number of nucleotide in the conventional DNA molecule at least 10 times higher than the number of genes. Such a "redundancy" of DNA is explained by the fact that, for example, in a person, only 6-10% of the entire DNA makes the coding specific nucleotide sequences, the remaining nucleotides in genetic coding are not directly involved.

Most eukaryot genes have an intermittent structure: a DNA section encoding the amino acid sequence of a protein polypeptide chain, separated by the sequential inserts into several parts. In addition, some uncommon nucleotide sequences frame the transcribed unit from the ends. When transcription and those and other DNA sections are "read" in the form of a single molecule predecessor of mRNA. Then the uncomfortable areas are knocked out, and the encoder sites are connected to each other, forming the molecule "mature" mRNA, which can be translated into the protein molecule. Other unknown nucleotide sequences can play the role of signal sequences responsible for the beginning of certain processes in the cell. These include the so-called transcription promoters, the dunging replication points, chromosome twisting areas, and others. Singing sequences consist of a variety of families characterized by varying degrees of recipes for nucleotides and various organizations. However, only a few of these sequences are studied so much so that a certain sequence can be attributed to a certain one.

Thus, the gene is a complex microsystem that ensures the vital activity of the cell and the body in. The theory of the gene, constantly deepening and developing, is the basis of genetic engineering (genetic engineering) , the ultimate goal of which is the creation of organisms with new hereditary properties, as well as the development of methods for the treatment of genetically determined diseases (see hereditary diseases) .