Elements of the correct answer

1. Each organism is individual in its hereditary characteristics, this also applies to the structure of proteins.

2. When transplanting organs and tissues, there is a threat of their rejection due to the incompatibility of the proteins of the donor and recipient.

Answer yourself

What is the relationship between genes and body proteins?

What and how does a gene encode?

Elements of the correct answer

1. It is necessary that the gene responsible for the phenotypic trait be inherited by the organism.

2. It is necessary that the gene was either dominant or recessive, but in this case it was in a homozygous state.

Answer yourself

What conditions contribute to the variability of the body?

How are variability and heredity related?

Elements of the correct answer

1. Inherited traits do not always appear, for example, a trait may be recessive and be in a heterozygous state.

2. The manifestation of phenotypic traits depends on many factors (for example, penetrance and expressivity of genes), therefore, despite the presence of the corresponding genes, an inherited trait may not appear.

Answer yourself

What is the relationship between the genotype and phenotype of an organism?

Is it possible to determine its genotype by the phenotype of an organism? Justify the answer.

Elements of the correct answer

1. These plants differ from each other in one feature - the shape of the seeds.

2. This trait is controlled by one pair of allelic genes.

Answer yourself

Why is the crossing of pea plants with yellow and smooth seeds with plants producing green and wrinkled seeds called a dihybrid?

Why in the first generation with monohybrid crossing the sign of seed wrinkling does not appear?

Elements of the correct answer

1. In hybrids of the first generation, only a dominant trait appears.

2. The recessive trait in these hybrids is suppressed.

Answer yourself

How is Mendel's first law formulated?

Why, according to Mendel's first law, in F2 (offspring from crossing F1 hybrids) is the splitting approximately equal to 3:1?

Elements of the correct answer

1. Mendel's laws are statistical in nature, i.e. confirmed on a large number of individuals (large statistical sample).

2. In real life, in organisms that give a small number of descendants, there are deviations from Mendel's laws due to statistics.

3. Incomplete dominance, non-allelic gene interactions are possible.

Answer yourself

Are Mendel's laws valid in families with two or three children? Explain the answer.

How can one explain that children in the same family inherit different traits from their parents?

Elements of the correct answer

1. Pea is a plant with pronounced contrasting allelic traits.

2. Pea is a self-pollinating plant, which allows you to experiment with clean lines and conduct artificial cross-pollination.

Answer yourself

What patterns underlie splitting by genotype and phenotype in monohybrid crossing?

What patterns underlie splitting by genotype and phenotype in dihybrid crosses?

What is the essence of the gamete purity hypothesis?

Elements of the correct answer

1. A donkey and a horse have different karyotypes (a donkey has 62 chromosomes, a horse has 64). Horse chromosomes are not homologous to donkey chromosomes.

2. Different chromosomes in meiosis do not conjugate with each other. Therefore, hybrids - mules - are sterile.

Answer yourself

Why is the number and nucleotide composition of chromosomes considered a species characteristic of organisms?

What is the biological meaning of chromosome conjugation and crossing over?

Elements of the correct answer

1. With complete dominance, heterozygous individuals in the phenotype show a dominant trait (plant with red flowers? plant with white flowers = plant with red flowers: AA x aa = Ah;Ah- red flowers).

2. With incomplete dominance in the heterozygous state, an intermediate phenotype appears (plant with red flowers? plant with white flowers = plant with pink flowers: AA x aa = Ah;Ah- pink flowers).

Answer yourself

In what cases is the intermediate nature of inheritance manifested?

Can we say that the phenomenon of incomplete dominance refutes the hypothesis of gamete purity?

Elements of the correct answer

Gametes of one organism AB, Ab; another - AB, aB.

Answer yourself

What types of gametes does an individual with a genotype give СсВbКК?

Write in the Punnett lattice the results of crossing heterozygous individuals for two traits.

Elements of the correct answer

1. Analyzing crossing is carried out to establish the genotype of a certain individual - to identify a recessive gene in it.

2. To do this, an individual homozygous for the recessive gene is crossed with an individual whose genotype is unknown.

Answer yourself

Is it possible to determine the genotype of an individual from the phenotype? Explain the answer.

How can you accurately determine the genotype of an individual?

Elements of the correct answer

1. The law is valid for genes located on one chromosome.

2. The law is violated when crossing over homologous chromosomes.

Answer yourself

Under what conditions does crossover occur?

Which chromosomes do not cross over?

What are the causes of combinative variability?

Elements of the correct answer

1. These structures include mitochondria, chloroplasts, cell center.

2. These organelles contain DNA.

Answer yourself

Is there a heredity that is not transmitted through the chromosomal apparatus of the cell?

What do the nucleus, mitochondria and chloroplasts have in common?

Elements of the correct answer

1. Sex is determined by a pair of sex chromosomes located in human nuclear cells.

2. For men, this pair consists of a set denoted XY, among women - XX.

Answer yourself

What is homo- and heterogamety?

How is sex-linked inheritance manifested?

Why are there no tortoiseshell cats?

Elements of the correct answer

1. Closely related marriages.

2. Age of the woman giving birth to a child (38–42 years).

3. The work of parents in hazardous enterprises (nuclear, chemical, etc.).

Answer yourself

What risks of an increase in the frequency of hereditary diseases can you name? Explain your choice.

How is Down syndrome manifested and what are the causes of this disease?

Elements of the correct answer

1. Gene mutations affect one of the sections of the gene. For example, one nucleotide in a triplet can drop out or be replaced. A mutation can be neutral, or it can be harmful or beneficial.

2. Chromosomal mutations can lead to serious health consequences. They are associated with rearrangement of chromosomes.

3. Genomic mutation affects the genome. As a result of such a mutation, the number of chromosomes in the karyotype changes. If one or more haploid sets are added to the chromosome set, then the phenomenon is called polyploidy. The phenomenon of polyploidy makes it possible to overcome interspecific sterility.

C2 questions

Typically, questions on genetics are not found in the examination papers of the USE at the C2 level. However, we present tasks corresponding to this level for better assimilation of genetic concepts by schoolchildren.

Elements of the correct answer

Mistakes were made in sentences 2, 5, 6.

Sentence 2 erroneously indicates the number of features by which the plants differed.

In sentence 5, the percentage of hybrids with yellow seeds is erroneously indicated.

In sentence 6, the sign of yellow color is erroneously named.

2. 1. There is reproductive isolation between species. 2. This factor contributes to the preservation of the species as an independent evolutionary unit. 3. It is especially important that genetically distant species be isolated. 4. The possibility of crossing between them is higher than with closely related species. 5. Protection from foreign genes is achieved: a) by different maturation of gametes, b) by similar habitats, c) by the ability of the egg to distinguish between its own and foreign spermatozoa. 6. Interspecific hybrids are often not viable or sterile.

Elements of the correct answer

Mistakes were made in sentences 3, 4, 5.

In sentence 3, there is an error in indicating the nature of the genetic proximity of species.

Proposition 4 erroneously states the probability of interbreeding between certain species.

In sentence 5, one of the factors of protection against foreign genes is incorrectly named.

3. Find errors in the given text. Specify the numbers of proposals in which they are allowed, explain them. 1. A gene is a section of an mRNA molecule that determines the structure of a protein and the corresponding feature of an organism. 2. Somatic cells contain a haploid set of chromosomes. 3. Genes that store information about one trait are located in strictly defined regions of homologous chromosomes and are called allelic. 4. Individuals that carry two identical allelic genes and give the same gametes are called dominant. 5. Individuals carrying allelic genes of different manifestations and, accordingly, different gametes, are called heterozygous. 6. Patterns of independent inheritance of traits were established by T. Morgan.

Elements of the correct answer

Mistakes were made in sentences 1, 2, 4, 6.

Sentence 1 has an erroneous definition of a gene.

Sentence 2 erroneously indicates the set of chromosomes in somatic cells.

Proposition 4 incorrectly defines dominance.

Elements of the correct answer

Errors were made in the recording of gametes formed by the parental individuals and in the recording of one of the genotypes.

Correct the mistakes made using the Punnett lattice.

5. Find errors in the given text. Specify the numbers of proposals in which they are allowed, explain them. 1. Gene - a section of the chromosome that encodes information about the sequence of amino acids in one protein molecule. 2. Transmitted from parents to children, genes change (mutate). 3. The totality of all the genes of an organism is called a phenotype. 4. The totality of all external and internal features of an organism is called the genotype. 5. It is not so much the sign itself that is inherited, but the possibility of its manifestation. 6. The realization of a trait depends both on the genotype and on the conditions of the environment in which the organism is formed.

Elements of the correct answer

Mistakes were made in sentences 2, 3, 4.

Sentence 2 erroneously indicates the nature of the transfer of genes from parents to offspring.

Sentence 3 incorrectly defines the phenotype.

Sentence 4 incorrectly defines the genotype.

Elements of the correct answer

1. An entry in a gene expression has letter designations.

2. The record in chromosomal expression is shown in alphabetical and graphical form.

Answer yourself

Find the error in the problem statement.

In dogs, the trait of black coat color is dominant over the trait of brown color. When crossing two black dogs, they got black and brown puppies. In the second generation, 3 black and 2 brown puppies were obtained from brown parents. What are the genotypes of the first pair of parents?

Find errors in the given text.

Two sons were born in the family of a retired hussar colonel Ivan Aleksandrovich Prilezhaev. The boys grew up as energetic children, participated in all boyish amusements. However, the trouble is that one of them, Peter, suffered from hemophilia, while Stepan did not have it. The boys' mother, Polina Arkadyevna, blamed her husband for Petenka's illness. Ivan Alexandrovich did not consider himself guilty. When the boys grew up, then, according to tradition, they had to go to serve in the hussars. However, both were rejected by the medical department, telling their father that the guys had a heavy heredity and it was impossible to serve them. Any scratch is dangerous for both, and even more so for injury. After some time, Peter married a girl who was healthy on the basis of hemophilia, in whose family there were no hereditary diseases. They had two boys and two girls. All children suffered from hemophilia. Stepan also married - to the second daughter from the same family. He had a hemophilic boy and two healthy girls. Nothing is known about the health of the grandchildren in this family.

What process is shown in the picture? Name the resulting gametes and explain the reason for the appearance of different gametes.

C6 level questions

Tasks for monohybrid crossing

Algorithm for solving problems in genetics

1. Select the letter designations of alleles.

2. Write down all given conditions of the problem.

3. Write the genotypes of the crossing individuals.

4. Write the types of gametes formed in the parents.

5. Write down the genotypes and phenotypes of the offspring.

The most important condition for the correct solution of the problem is a complete understanding of what is known and what is being asked. For example, if the condition says that 9 mice were obtained from two gray mice, of which one or two were white, then this means that both parents were heterozygous for the dominant trait of gray color, and the white color of the coat is a recessive trait. This example shows how, based on the condition of the problem, to display the data necessary to solve it. Having understood the meaning of the problem and having received additional data from its condition, correctly write down the solution. In the given task, the entry will look like this:

If the problem does not ask about the splitting of traits in the offspring in terms of ratio, then you do not need to show it. It is enough to represent all possible genotypes in F1.

Examples of simple tasks

1. What F1 offspring can be expected from crossing a red-flowered heterozygous pea plant ( A) with a white-flowered plant? Will splitting of signs be observed and in what ratio?

2. From Drosophila flies with normal wings and flies with shortened wings, flies with normal and shortened wings were obtained in a ratio of 1:1. Determine the genotypes of parents and offspring.

3. The black plumage of Andalusian chickens does not completely dominate the white plumage. A black-feathered rooster was crossed with a white-feathered hen. Some of the chickens born from this cross were blue-feathered. Write down the genotypes of all the individuals mentioned in the condition. What splitting by genotype and phenotype should be expected in the offspring from these parents, provided that there are enough chickens? Is it possible to breed a pure line of chickens with blue feathers?

4. When crossing two tall ( WITH) plants, 25% of the seeds were obtained, from which stunted plants grew. What are the genotypes of low growing plants?

Tasks for dihybrid crossing

When solving problems of this type, it is necessary:

a) carefully read the condition of the problem;
b) in the course of reading the problem, make the necessary notes;
c) having understood the condition of the problem, it is necessary to designate the alleles with the corresponding letters, draw the Punnett lattice and fill it in accordance with the logic of the solution;
d) make sure that the general form of the decision record meets the requirements.

An example of a problem discussed in textbooks

Pea plants producing yellow ( A) smooth ( IN) seeds, crossed with plants that give green ( A) wrinkled ( b) seeds. Both lines were clean. What will be the hybrid offspring in F1 and F2 in terms of genotypes and phenotypes?

The logic of reasoning is as follows.

1. If the lines are clean, then the parents are homozygous for both traits.

2. Each parent produces one variety of gametes.

Genotype AABB gives gametes AB.
Genotype aabb gives gametes ab.
Therefore, all first-generation hybrids will have the genotype AaBb.
Individuals with this genotype form 4 varieties of gametes: AB, aB, Ab, ab.

3. To determine the genotypes of individuals of the second generation, it is necessary to draw a Punnett lattice and write out the types of gametes formed by the parents in the upper horizontal line and the left vertical column. After that, in the remaining free fields, write down the resulting genotypes of the offspring.

	AABB and. ch.	AaBB and. ch.	AABb and. ch.	AABb and. ch.
	AaBB and. ch	aaBB h. ch.	AaBb and. ch.	aaBb h. ch.
	AABb and. ch	AaBb and. ch.	AAbb and. wrinkles	Aabb and. wrinkles
	AaBb and. ch.	aaBb h. ch.	Aabb and. wrinkles	aabb h. wrinkles

– both dominant genes;
- the dominant gene of one of the traits;
- dominant gene of another trait;
- only recessive genes.

The result in this case will be as follows: 9 AB : 3Ab : 3aB : 1ab.

5. Answer: hybrid offspring in F1 - AaBb, in the second generation there will be 16 genotypes (shown in the Punnett grid) and 4 phenotypes:

- plants with yellow smooth seeds;
- plants with yellow wrinkled seeds;
- plants with green smooth seeds;
- plants with green wrinkled seeds.

Tasks encountered in examination papers

Elements of the correct answer

For a correct solution, you need to prove that:

1) flies with the genotype XY(males) can be red-eyed and white-eyed;
2) heterozygous females are always red-eyed, females homozygous for a recessive trait are white-eyed, and females homozygous for a dominant trait are red-eyed.

To prove these two positions, it is necessary to cross a red-eyed heterozygous female with a white-eyed male. Some males from this cross will have white eyes. Therefore, the recessive trait is linked to X-chromosome.

2. Make a diagram illustrating the text below, showing the genotypes and inheritance patterns of color blindness. If a woman suffering from color blindness marries a man with normal vision, then their children have a very peculiar pattern of cross-inheritance. All daughters from such a marriage will receive the sign of the father, i.e. they have normal vision, and all the sons, receiving the sign of the mother, suffer from color blindness (a-color blindness linked to X-chromosome). In the same case, when the father is color blind and the mother has normal vision, all children are normal. In some marriages in which mother and father have normal vision, half of the sons may be affected by color blindness. Color blindness is more common in men.

Elements of the correct answer

Girls are carriers, boys are color blind.

Girls are carriers, boys are healthy.

Half of the boys and girls are healthy, half of the girls are carriers, half of the boys are color blind.

Elements of the correct answer for independent decision

1. Write down the letter designations of the alleles of the genotypes of the parents and the crossing pattern.

2. Determine all genotypes specified in the condition.

3. Draw up a diagram of a new cross and write down its results.

Elements of the correct answer

1. Genotypes of parents X f X And XY.

2. Genotypes of children X f Y, X f X, XX, XY.

3. The nature of inheritance is dominant, linked to X-chromosome.

Elements of the correct answer

1. According to the condition, the baldness gene was inherited only by boys.

2. All women in the considered families had normal hair.

3. Therefore, this gene was transmitted from fathers, i.e. along the male line.

4. Conclusion: the trait is linked to At chromosome and is passed from fathers to sons.

P1 XY l x XX
F1 2 XY l and 4 XX
P2 XY l x XX
F2 Grandchildren XY l

Decide for yourself

Draw a diagram to illustrate the text below, showing the genotypes and inheritance patterns of hemophilia.

An example of sex-linked inheritance is the inheritance of a recessive semi-lethal gene that causes blood incoagulability in air - hemophilia. This disease appears almost exclusively in boys. With hemophilia, the formation of a factor that accelerates blood clotting is disrupted. The recessive gene that controls the synthesis of this factor is located in a certain area X- chromosomes and does not have an allele in At-chromosome. After solving the problem, answer the question: “Why are women with hemophilia extremely rare?”
Write down the results of crossing, which can be obtained in the following cases:

a) the father is a hemophiliac, the mother is a carrier of the hemophilia gene;
b) the father is healthy, the mother is a carrier of the hemophilia gene;
c) the father is hemophilic, the mother does not carry the hemophilia gene.

In humans, large eyes and a Roman nose (with a hump) dominate over small eyes and a Greek (straight) nose. A woman with big eyes and a Greek nose married a man with small eyes and a Roman nose. They had four children, two of whom had large eyes and a Roman nose. What are the genotypes of the parents? What is the probability that this couple will have a child with small eyes and a Roman nose? What is the probability that this couple will have a child with small eyes and a Greek nose?

After the discovery of the principle of molecular organization of a substance such as DNA in 1953, molecular biology began to develop. Further, in the process of research, scientists found out how DNA is recombined, its composition, and how our human genome is arranged.

Every day, at the molecular level, complex processes take place. How is the DNA molecule arranged, what does it consist of? What role do DNA molecules play in a cell? Let's talk in detail about all the processes occurring inside the double chain.

What is hereditary information?

So how did it all start? Back in 1868 found in the nuclei of bacteria. And in 1928, N. Koltsov put forward the theory that it is in DNA that all genetic information about a living organism is encrypted. Then J. Watson and F. Crick found a model for the now well-known DNA helix in 1953, for which they deserved recognition and an award - the Nobel Prize.

What is DNA anyway? This substance consists of 2 combined threads, more precisely spirals. A section of such a chain with certain information is called a gene.

DNA stores all the information about what kind of proteins will be formed and in what order. A DNA macromolecule is a material carrier of incredibly voluminous information, which is recorded in a strict sequence of individual building blocks - nucleotides. There are 4 nucleotides in total, they complement each other chemically and geometrically. This principle of complementation, or complementarity, in science will be described later. This rule plays a key role in encoding and decoding genetic information.

Since the DNA strand is incredibly long, there are no repetitions in this sequence. Every living being has its own unique DNA strand.

Functions of DNA

The functions include the storage of hereditary information and its transmission to offspring. Without this function, the genome of a species could not be preserved and developed over millennia. Organisms that have undergone major gene mutations are more likely to not survive or lose their ability to produce offspring. So there is a natural protection against the degeneration of the species.

Another essential function is the implementation of stored information. The cell cannot make any vital protein without the instructions that are stored in the double strand.

Composition of nucleic acids

Now it is already reliably known what the nucleotides themselves, the building blocks of DNA, consist of. They include 3 substances:

• Orthophosphoric acid.
• nitrogenous base. Pyrimidine bases - which have only one ring. These include thymine and cytosine. Purine bases containing 2 rings. These are guanine and adenine.
• Sucrose. DNA contains deoxyribose, RNA contains ribose.

The number of nucleotides is always equal to the number of nitrogenous bases. In special laboratories, a nucleotide is cleaved and a nitrogenous base is isolated from it. So they study the individual properties of these nucleotides and possible mutations in them.

Levels of organization of hereditary information

There are 3 levels of organization: gene, chromosomal and genomic. All the information needed for the synthesis of a new protein is contained in a small section of the chain - the gene. That is, the gene is considered the lowest and simplest level of encoding information.

Genes, in turn, are assembled into chromosomes. Thanks to such an organization of the carrier of hereditary material, groups of traits alternate according to certain laws and are transmitted from one generation to another. It should be noted that there are incredibly many genes in the body, but information is not lost, even when it is recombined many times.

There are several types of genes:

• according to their functional purpose, 2 types are distinguished: structural and regulatory sequences;
• according to the influence on the processes occurring in the cell, there are: supervital, lethal, conditionally lethal genes, as well as mutator and antimutator genes.

Genes are arranged along the chromosome in a linear order. In chromosomes, information is not randomly focused, there is a certain order. There is even a map showing positions, or gene loci. For example, it is known that data on the color of the eyes of a child is encrypted in chromosome number 18.

What is a genome? This is the name of the entire set of nucleotide sequences in the cell of the body. The genome characterizes the whole species, not a single individual.

What is the human genetic code?

The fact is that the whole huge potential of human development is laid down already in the period of conception. All hereditary information that is necessary for the development of the zygote and the growth of the child after birth is encrypted in the genes. Sections of DNA are the most basic carriers of hereditary information.

Humans have 46 chromosomes, or 22 somatic pairs plus one sex-determining chromosome from each parent. This diploid set of chromosomes encodes the entire physical appearance of a person, his mental and physical abilities and predisposition to diseases. Somatic chromosomes are outwardly indistinguishable, but they carry different information, since one of them is from the father, the other is from the mother.

The male code differs from the female code in the last pair of chromosomes - XY. The female diploid set is the last pair, XX. Males get one X chromosome from their biological mother, and then it is passed on to their daughters. The sex Y chromosome is passed on to sons.

Human chromosomes vary greatly in size. For example, the smallest pair of chromosomes is #17. And the biggest pair is 1 and 3.

The diameter of the double helix in humans is only 2 nm. The DNA is so tightly coiled that it fits in the small nucleus of the cell, although it will be up to 2 meters long if unwound. The length of the helix is ​​hundreds of millions of nucleotides.

How is the genetic code transmitted?

So, what role do DNA molecules play in a cell during division? Genes - carriers of hereditary information - are inside every cell of the body. In order to pass on their code to a daughter organism, many creatures divide their DNA into 2 identical helices. This is called replication. In the process of replication, DNA unwinds and special "machines" complete each chain. After the genetic helix bifurcates, the nucleus and all organelles begin to divide, and then the whole cell.

But a person has a different process of gene transfer - sexual. The signs of the father and mother are mixed, the new genetic code contains information from both parents.

The storage and transmission of hereditary information is possible due to the complex organization of the DNA helix. After all, as we said, the structure of proteins is encrypted in genes. Once created at the time of conception, this code will copy itself throughout life. The karyotype (personal set of chromosomes) does not change during the renewal of organ cells. The transmission of information is carried out with the help of sex gametes - male and female.

Only viruses containing a single strand of RNA are unable to transmit their information to their offspring. Therefore, in order to reproduce, they need human or animal cells.

Implementation of hereditary information

Important processes are constantly taking place in the cell nucleus. All information recorded in chromosomes is used to build proteins from amino acids. But the DNA strand never leaves the nucleus, so another important compound, RNA, is needed here. Just RNA is able to penetrate the nuclear membrane and interact with the DNA chain.

Through the interaction of DNA and 3 types of RNA, all encoded information is realized. At what level is the implementation of hereditary information? All interactions occur at the nucleotide level. Messenger RNA copies a segment of the DNA chain and brings this copy to the ribosome. Here begins the synthesis of the nucleotides of a new molecule.

In order for the mRNA to copy the necessary part of the chain, the helix unfolds and then, upon completion of the recoding process, is restored again. Moreover, this process can occur simultaneously on 2 sides of 1 chromosome.

The principle of complementarity

They consist of 4 nucleotides - these are adenine (A), guanine (G), cytosine (C), thymine (T). They are connected by hydrogen bonds according to the rule of complementarity. The works of E. Chargaff helped to establish this rule, since the scientist noticed some patterns in the behavior of these substances. E. Chargaff discovered that the molar ratio of adenine to thymine is equal to one. And in the same way, the ratio of guanine to cytosine is always equal to one.

Based on his work, geneticists have formed a rule for the interaction of nucleotides. The rule of complementarity states that adenine combines only with thymine, and guanine with cytosine. During the decoding of the helix and the synthesis of a new protein in the ribosome, this alternation rule helps to quickly find the necessary amino acid that is attached to the transfer RNA.

RNA and its types

What is hereditary information? nucleotides in the DNA double strand. What is RNA? What is her job? RNA, or ribonucleic acid, helps to extract information from DNA, decode it, and, based on the principle of complementarity, create proteins necessary for cells.

In total, 3 types of RNA are isolated. Each of them performs strictly its function.

1. Informational (mRNA), or it is also called matrix. It goes right into the center of the cell, into the nucleus. It finds in one of the chromosomes the necessary genetic material for building a protein and copies one of the sides of the double chain. Copying occurs again according to the principle of complementarity.
2. Transport is a small molecule that has nucleotide decoders on one side, and amino acids corresponding to the main code on the other side. The task of tRNA is to deliver it to the "workshop", that is, to the ribosome, where it synthesizes the necessary amino acid.
3. rRNA is ribosomal. It controls the amount of protein that is produced. Consists of 2 parts - amino acid and peptide site.

The only difference when decoding is that RNA does not have thymine. Instead of thymine, uracil is present here. But then, in the process of protein synthesis, with tRNA, it still correctly establishes all the amino acids. If there are any failures in the decoding of information, then a mutation occurs.

Repair of a damaged DNA molecule

The process of repairing a damaged double strand is called reparation. During the repair process, damaged genes are removed.

Then the required sequence of elements is exactly reproduced and crashes back into the same place on the chain from where it was extracted. All this happens thanks to special chemicals - enzymes.

Why do mutations occur?

Why do some genes begin to mutate and cease to fulfill their function - the storage of vital hereditary information? This is due to a decoding error. For example, if adenine is accidentally replaced with thymine.

There are also chromosomal and genomic mutations. Chromosomal mutations occur when pieces of hereditary information are missing, duplicated, or even transferred and integrated into another chromosome.

Genomic mutations are the most serious. Their cause is a change in the number of chromosomes. That is, when instead of a pair - a diploid set, a triploid set is present in the karyotype.

The most famous example of a triploid mutation is Down syndrome, in which the personal set of chromosomes is 47. In such children, 3 chromosomes are formed in place of the 21st pair.

There is also such a mutation as polyploidy. But polyploidy is found only in plants.

Think about the structure of proteins. What determines the structure, shape and properties of a protein molecule? Why are the proteins of each organism different from each other?

Such signs of the living as self-reproduction, heredity and variability are already manifested at the molecular-genetic level. They are associated with certain organic matter and with the hereditary (genetic) program of the body.

DNA and genes. By the beginning of the 50s. 20th century scientists suggested that the main function of genes is to determine the structure of proteins, primarily enzyme proteins. Numerous studies have shown that, in general, the transformations of substances in living systems occur under the control of enzymes. Therefore, scientists have put forward an assumption that can be formulated as follows: "one gene - one protein-enzyme." Only the discovery of the double helix of the DNA molecule made it possible to elucidate the general principles of the process of transmission of genetic information in living things.

DNA molecules serve as carriers of hereditary information. They store information about the structure. properties, functions of proteins of each cell and the organism as a whole. A section of a DNA molecule containing information about the structure of one protein-enzyme molecule was called a gene (from the Greek genos - genus, origin). It is the hereditary factor of any living body of nature.

Genetic code. There are 20 amino acids in proteins, the sequence of which determines the structure and properties of proteins. Information about the structure of a protein must be recorded as a nucleotide sequence on DNA. The rules for translating a nucleotide sequence in a nucleic acid into an amino acid sequence of a protein are called the genetic code (from the French code - a collection of conventional abbreviations and names).

It was deciphered in the 60s. 20th century as a result of a series of experiments and mathematical calculations.

The DNA molecule consists of a set of four nucleotides (A, T, G, C). If each amino acid had a corresponding nucleotide, then only 4 amino acids could be encoded. If we assume that one amino acid is encoded by a combination of two nucleotides, then in this case only 42 = 16 amino acids can be encoded. Scientists suggested that one amino acid should be encoded by three nucleotides. This number of combinations is more than enough to encode 20 amino acids (Fig. 29). In addition, not one, but several such combinations can correspond to one amino acid.

Rice. 29. The rule for converting a nucleotide sequence in DNA into an amino acid sequence in a protein

The genetic code has a number of properties (Fig. 30). The code is intertwined - each amino acid corresponds to a combination of 3 nucleotides. In total, there are 64 such combinations - triplets (codons). Of these, 61 are sense triplets, that is, they correspond to 20 amino acids, and 3 are meaningless stop codons that do not correspond to amino acids. They fill the gaps between genes.

Rice. 30. Some properties of the genetic code

The code is unambiguous - each triplet (codon) corresponds to only one amino acid. The code is degenerate (redundant) - there are amino acids that are encoded by more than one triplet (codon). Most amino acids have 2-3 triplets (codons).

The code is universal - all organisms have the same genetic code, i.e. the same amino acids in different organisms are encoded by the same triplets (codons).

The code is continuous - there are no gaps between triplets (codons) inside the gene.

The code is non-overlapping - the final nucleotide of one triplet (codon) cannot serve as the beginning of another.

The amino acid sequence of a single protein molecule is encoded in a certain section of the DNA molecule using the genetic code. Since protein synthesis occurs in the cytoplasm, and DNA molecules are located in the nucleus, a structure is needed that would copy the nucleotide sequence on DNA and transfer it to the site of protein synthesis. Messenger RNA serves as such an intermediary.

In addition to the information carrier, substances are needed that would ensure the delivery of the corresponding amino acids to the site of synthesis and determine their places in the polypeptide chain. Transfer RNAs are such substances. They not only ensure the delivery of amino acids to the place of synthesis, but also their coding. Protein synthesis proceeds on ribosomes, for the assembly of which another type of nucleic acids is required - ribosomal RNA. Consequently, for the realization of hereditary information in living things at the molecular genetic level, DNA molecules and all types of RNA are needed.

Lesson learned exercises

1. Why were the hereditary properties of an organism originally associated with proteins?
2. How is the structure of a protein encoded in a DNA molecule?
3. What is a gene?
4. What is the genetic code? Describe each of its properties.
5. What is the function of stop codons?

Heredity, ideas about the genetic code, personality genes.

Annotation................................................. ................................................. ........................3

Foreword ..........................................................................................................................4

Heredity ............................................................................................................6

Conditioned reflexes ........................................................................................................7

Weismann's theory of heredity .........................................................................8

Galton Methods .........................................................................................................9

Chromosomal theory of heredity ..................................................................10

Genetic maps of chromosomes ..................................................................................10

Sex Genetics ...............................................................................................................13

Nonchromosomal theory of heredity .........................................................14

Molecular genetics. genetic information . Genetic code .....14

Heredity and evolution ..................................................................................17

human genetics .......................................................................................................19

Heredity and environment .............................................................. ........................................20

Diseases associated with mutations ............................................................... ...............................21

Treatment and prevention of hereditary diseases ..............................................24

Genetic engineering .................................................................. .........................................25

Personality genes ............................................................................................28

Conclusion .......................................................................................................................30

Terminological dictionary .........................................................................................32

List used literature ............................................................................36

annotation

In his term paper on the topic “Heredity. Ideas about the genetic code. Personality genes ”I talked about the first steps of genetics, about the present day of this fascinating science and what we expect from it in the near future. The achievements of modern genetics at the molecular level were also considered in detail, which includes biology and genetics, the laws of transmission of hereditary traits and the structure of the genetic substance, the structure and functions of the gene, genes and the consistency of cellular functions, heredity and evolution. This work introduces the enormous contribution of genetics to neighboring areas of biology - the study of the origin of life, the systematics and evolution of organisms.

Foreword

From time immemorial, man has sought to find out why similar organisms are born from living organisms? And at the same time, there is no absolute similarity between parents and offspring, either in physical characteristics or in character.

Now it is obvious that the similarity of parents and descendants of organisms of the same species is determined by heredity, and their distinctive features are determined by variability. Two properties - heredity and variability - are characteristic not only for humans, but for all life on Earth. The study of these most important properties of living beings is the science called genetics .

Of course, at first glance it seems. that we can all live quite calmly without knowing the essence of the secrets of heredity, and that all this is unimportant. But is it really so?

How, without knowing genetics, to explain why a monkey does not turn into a polar bear, even if it is settled in the Far North, and why a polar bear, even if it was born in a zoo somewhere in the south, still remains white? Will agricultural workers be able to get hundreds of centners of wheat per hectare in the near future? Will the consequences of atomic explosions affect the descendants of the modern inhabitants of Hiroshima and Nagasaki in some 50-100 years? Why do children look like their parents? Is humanity threatened with extinction, or are we at the beginning of the development of earthly civilization? Why, without human intervention, rye remains rye, and wheat remains wheat? What are the causes of hereditary diseases and how to deal with them? How long can a person live? Can all people on Earth be geniuses?

There are still thousands and thousands of similar questions, which are of great importance both for individuals and for the whole of humanity, which cannot be answered,

without knowing the secrets of heredity and without learning how to manage it. When a person reveals all these secrets and puts knowledge to his own advantage, he will be able to participate in solving the practical problems of agriculture, medicine, and learn to control the evolution of life on our planet as a whole.

However, we must not forget. that for the spiritual life and purposeful activity of modern man, the scientific worldview is of paramount importance. Among the philosophical questions of the new natural science, one of the main ones is understanding the essence of life, its place in the universe. And only modern molecular genetics has been able to show that life is a truly material, self-developing phenomenon. reflecting the influence of environmental conditions.

But she also proved that life has a system. which cannot be decomposed into its constituent physicochemical processes. However. modern science does not yet fully know the essence of life.

One more question: on what does the present and future of mankind depend? This problem interested people many centuries ago and no less excites today. This is not surprising, since a person differs from the entire surrounding world in the first place by the fact that he is influenced not only by biological laws. Its future is no less, if not more, dependent on the social reorganization of the world.

Human hereditary information is passed from generation to generation. All biological features that served as the basis for the emergence of a person with consciousness are encoded in hereditary structures, and their transmission to generations is a prerequisite for the existence of a person on Earth as a rational being. Man as a biological species is the highest and at the same time unique “achievement” of evolution on our planet. And as yet, no one can say with certainty or provide irrefutable evidence that this does not apply to the entire universe.

Evolution on Earth sometimes goes slowly, sometimes it undergoes leaps, each of which elevates a given branch of organisms to a new level. Among the many leaps-revolutions in the history of life on Earth, two, apparently, should be considered the main ones. First, the transition from the inorganic world to the organic, that is, the emergence of life, and

second, the emergence of consciousness, that is, the emergence of man. Both of these phenomena are associated with the accumulation of quantitative changes. causing qualitative changes.

“ No matter how humanity goes along the path of progress, our xx century. will forever remain in his memory. People will always remember that this century was marked by three major achievements; people learned to use the energy of the atom, went into space and began to purposefully change heredity. These are the three great successes that our distant descendants will remember even when they fly from star to star and conquer old age and death.”

But if the prospects of nuclear physics are taught at school, if we know the astronauts by sight thanks to television, things are worse with biology. Its greatest achievements have not yet become known to the masses.

The foundations of genetics were laid by the Czech scientist Gregor Mendel in experiments, the results of which were published in 1865. Since then, genetics has not stopped in its development. I. M. Sechenov, A. P. Bogdanov, N. K. Koltsov, G. Sade, Avery, McLeod, McCarthy, D. Watson - these are some of those great scientists who made a huge contribution to the science of heredity.

IN last years against the background of a general decrease in morbidity and mortality, the proportion of congenital and hereditary diseases increased. In this regard, the role of genetics in practical medicine has increased significantly.” Without knowledge of genetics, it is impossible to effectively diagnose hereditary and congenital diseases.”

Heredity - the property inherent in all organisms to repeat the same signs and features of development in a number of generations; due to the transfer in the process of reproduction from one generation to another of the material structures of the cell, containing programs for the development of new individuals from them. Thus, heredity ensures the continuity of the morphological, physiological and biochemical organization of living beings, the nature of their individual development, or ontogeny. As a general biological phenomenon, heredity is the most important condition for the existence of differentiated forms of life, signs of organisms, although it is violated variability- the emergence of differences between organisms. Affecting a wide variety of traits at all stages of the ontogeny of organisms, heredity manifests itself in the patterns of inheritance of traits, that is, their transmission from parents to descendants.

Sometimes the term heredity refers to the transmission from one generation to another of infectious principles (the so-called. infectious heredity) or learning skills, education, traditions (so-called. social, or signal inheritance). A similar extension of the concept

heredity beyond its biological and evolutionary nature is debatable. Only in cases where infectious agents are able to interact with host cells up to inclusion in their genetic apparatus, it is difficult to separate infectious heredity from normal.

Conditioned reflexes . As we know, conditioned reflexes are individually acquired complex adaptive reactions of the organism of animals and humans, arising under certain conditions (hence the name) on the basis of the formation of a temporary connection between a conditioned (signal) stimulus and an unconditional reflex act that reinforces this stimulus. Conditioned reflexes are not inherited, but are developed anew by each generation, however, the role of heredity in the speed of fixing conditioned reflexes and behavioral patterns is indisputable. Therefore, the signal heredity includes a component of biological heredity.

Attempts to explain the phenomena of heredity, related to ancient times

(Hippocrates, Aristotle etc.) are of historical interest only. Only the discovery of the essence of sexual reproduction made it possible to clarify the concept of heredity and associate it with certain parts of the cell. By the middle of the 19th century. thanks to numerous experiments on plant hybridization (J. G. kelreuter etc.) data on the patterns of heredity are accumulated. In 1865 G. Mendel in a clear mathematical form reported the results of his experiments on hybridization of peas. These messages were later called Mendel's laws and formed the basis of the doctrine of heredity - Mendelism. Almost simultaneously, attempts were made to speculatively understand the essence of heredity. In the book "Changes in Domestic Animals and Cultivated Plants" Ch. Darwin(1868) proposed his “temporary hypothesis of pangenesis”, according to which their rudiments-gemmules are separated from all cells of the body, which, moving with the blood flow, settle in germ cells and formations that serve for asexual reproduction (kidneys, etc.). Thus, it turned out that germ cells and kidneys consist of a huge amount of gemmules. With the development of the organism, gemmules turn into cells of the same type from which they were formed. In hypothesis pangenesis unequal ideas are combined: about the presence in germ cells of special particles that determine the subsequent development of an individual; about their transfer from the cells of the body to the sex cells. The first position was fruitful and led to modern ideas about corpuscular inheritance. The second, which gave grounds for the notion of the inheritance of acquired traits, turned out to be incorrect. Speculative theories of heredity were also developed F. Galton, C. Negeli H. De Vries.

The most detailed speculative theory of heredity offered A. Weisman (1892). Based on the data accumulated by that time on fertilization, he recognized the presence in the germ cells of a special substance-carrier of heredity-germ plasm. Visible formations of the cell nucleus-chromosome-Weisman considered the highest units germplasm-idants.Idants consist of id located in the chromosome in the form of grains in a linear order. Ides consist of determinate, determining the type of cells during the development of an individual, and biofor, determining individual properties of cells. Ida contains all the determinants necessary to build the body of an individual of a given species. Germ plasm is contained only in germ cells; somatic, or body cells, are deprived of it. To explain this fundamental difference, Weisman assumed that in the process of cleavage of a fertilized egg, the main supply of germ plasm (and hence the determinate) enters one of the first cleavage cells, which becomes the parent cell of the so-called germline. In the rest of the cells of the embryo in the process of "unequal divisions" only a part of the determinates gets; finally, the determinants of one kind will remain in the cells, which determine the nature and properties of these particular cells. An essential property of the germ plasm is its great constancy. Weismann's theory turned out to be wrong in many details. However, his idea of ​​the role of chromosomes and the linear arrangement of the elementary units of heredity in them turned out to be correct and anticipated the chromosome theory of heredity. The logical conclusion from Weismann's theory is the denial of the inheritance of acquired traits. In all speculative theories of heredity, one can find individual elements that later found confirmation and more full development in the prevailing at the beginning of the 20th century. genetics. The most important of them:

a) isolation in the body of individual traits or properties, the inheritance of which can be analyzed by appropriate methods;

b) the determination of these properties by special discrete units of heredity, localized in the structures of the cell (nucleus) (Darwin called them gemmules, De Vries pangens, Weisman determinants). In modern genetics, the proposed by V. Johansen(1909) term gene .

“ Gene-elementary unit of heredity, representing a segment of the molecule of deoxyribonucleic acid - DNA (for some viruses - ribonucleic acid-RNA). Each gene determines the structure of one of the proteins of a living cell and thereby participates in the formation of a trait or properties of an organism..”

Galton Methods . Standing apart were attempts to establish patterns of heredity by statistical methods. One of the creators biometrics-F. Galton applied the methods of accounting for correlation and regression developed by him to establish a relationship between parents and descendants. He formulated the following laws of heredity (1889):

Regression, or return to the ancestors

Ancestral heredity, that is, the proportion of the heredity of ancestors in the heredity of descendants.

The laws are statistical in nature, they are applicable only to aggregates of organisms and do not reveal the essence and causes of heredity, which could only be achieved through experimental study of heredity by various methods, and above all hybridological analysis, the foundations of which were laid by Mendel. Thus, the patterns of inheritance of qualitative traits were established: monohybrid - the difference between crossed forms depends on only one pair of genes, dihybrid - on two, polyhybrid - on many. When analyzing the inheritance of quantitative traits, there was no clear picture of splitting, which gave reason to single out a special, so-called fused heredity and explain it by the displacement of the hereditary plasms of the crossed forms. Subsequently, hybridological and biometric analysis of the inheritance of quantitative traits showed that fused heredity is reduced to discrete, but the inheritance is polygenic. In this case, splitting is difficult to detect, since it occurs in many genes, the effect of which on the trait is complicated by the strong influence of environmental conditions. Thus, although signs can be divided into qualitative and quantitative, the terms "qualitative" and "quantitative" heredity are not justified, since both categories of heredity are fundamentally the same.

Development cytology led to the formulation of the question of the material foundations of heredity. For the first time, the idea of ​​the role of the nucleus as a carrier of heredity was formulated

ABOUT. Hertwig(1884) and E. Strasburger(1884) based on the study of the process of fertilization. T. Boveri(1887) established the individuality of chromosomes and developed a hypothesis about their qualitative difference. He, as well as E. van Benedet(1883) established a halving of the number of chromosomes during the formation of germ cells in meiosis. The American scientist W. Setton (1902) gave a cytological explanation of Mendel's law of independent inheritance of traits. However, the real rationale chromosome theory heredity was given in T. Morgana and his schools (since 1911), in which an exact correspondence between genetic and cytological data was shown. In experiments on Drosophila, a violation of the independent distribution of traits was established - their linked inheritance. This phenomenon was explained by the linkage of genes, that is, the location of the genes that determine these traits in one specific pair of chromosomes. Frequency study recombinations between linked genes crossing over) made it possible to map the location of genes on chromosomes.

Genetic maps of chromosomes - diagrams of the relative location of interlinked inheritances. factors - genes. Genetic maps of chromosomes reflect the real-life linear order of placement of genes in chromosomes and are important both in theoretical studies and in breeding work, because they allow you to consciously select pairs of traits during crossings, as well as predict the inheritance features and manifestations of various traits in the studied organisms . Having Genetic maps of chromosomes, it is possible to control the inheritance of the "signal" gene, closely linked to the one being studied. transfer to offspring of genes that determine the development of hard-to-analyze traits; for example, the gene for shriveled endosperm in maize, located on chromosome 9, is linked to a gene for reduced plant viability. Numerous facts of the absence (contrary to Mendel's laws) of independent distribution of recognition

kov in hybrids of the second generation were explained by the chromosome theory of heredity. Genes located on the same chromosome, in most cases, are inherited together and form one linkage group, the number of which, thus, corresponds to the haploid number of chromosomes in each organism. The American geneticist T. X. Morgan showed, however, that the linkage of genes located on the same chromosome in diploid organisms does not

absolute; in some cases, before the formation of germ cells between the same type, or homologous, chromosomes, there is an exchange of correspondences. plots; this process is called cross, or crossing over. The exchange of sections of chromosomes (with the genes in them) occurs with a different probability, depending on the distance between them (the farther apart the genes, the higher the probability of crossing over and, consequently, recombination). Genetic analysis makes it possible to detect a cross only when homologous chromosomes differ in the composition of genes, which, when crossing over, leads to the appearance of new gene combinations. Usually, the distance between genes on Genetic Chromosome Maps is expressed as a percentage of crossing over (the ratio of the number of mutant individuals that differ from their parents in a different combination of genes to the total number of individuals studied); the unit of this distance, the morganid, corresponds to a crossover frequency of 1%.

So let's select the main provisions of the chromosome theory of heredity :

1. Genes are located on chromosomes, different chromosomes contain an unequal number of genes, the set of genes of each of the non-homologous chromosomes is unique.

2. Genes in the chromosome are arranged linearly, each gene occupies a certain locus (place) in the chromosome.

3. Genes located on the same chromosome form a linkage group and together (linked) are transmitted to descendants, the number of linkage groups is equal to the haploid set of chromosomes.

4. Linkage is not absolute, since in the prophase of meiosis, crossing over can occur and genes located on the same chromosome are separated. The linkage strength depends on the distance between the genes in the chromosome: the greater the distance, the smaller the linkage strength. and vice versa. The distance between genes is measured as a percentage of crossing over. 1% crossover corresponds to one morganide.

Genetic maps of chromosomes are made for each pair of homologous chromosomes. Clutch groups are numbered sequentially as they are found. In addition to the number of the clutch group, indicate the full or abbreviated names. mutant genes, their distance in morganides from one of the ends of the chromosome, taken as a zero point, as well as the place centromeres. Genetic maps of chromosomes can be compiled only for objects in which a large number of mutant genes have been studied. For example, in Drosophila, more than 500 genes located in its 4 linkage groups have been identified, in maize, about 400 genes distributed in 10 linkage groups (Fig. 1). In less studied objects, the number of discovered linkage groups

less than the haploid number of chromosomes. Thus, about 200 genes have been identified in the house mouse, forming 15 linkage groups (in fact, there are 20 of them); in chickens, only 8 out of 39 have been studied so far. In humans, out of the expected 23 linkage groups (23 pairs of chromosomes), only 10 have been identified, and a small number of genes are known in each group; the most detailed maps are for the sex chromosomes.

Bacteria, to-rye are haploid organisms, have one, most often continuous, ring chromosome and all genes form one linkage group (fig. 2). When transferring genetic material from a donor cell to a recipient cell, for example, when conjugations, the ring chromosome breaks and the resulting linear structure is transferred from one bacterial cell to another (in Escherichia coli within 110-120 minutes). By artificially interrupting the conjugation process, it is possible to determine, by the types of recombinants that have arisen, which genes have managed to pass into the recipient cell. This is one of the methods for constructing genetic maps of bacterial chromosomes, which have been developed in detail in a number of species. Genetic maps of chromosomes of some bacteriophages

Sex Genetics . The number of groups of linked genes turned out to be equal to the number of pairs of chromosomes inherent in a given species. The most important evidence for the chromosome theory of heredity was obtained by studying sex-linked inheritance. Previously, cytologists discovered in the chromosome sets of a number of animal species special, so-called sex chromosomes in which females differ from males. In some cases, females have 2 identical sex chromosomes (XX), and males are different (XY), in others, males are 2 identical (XX, or ZZ), and females are different (XY, or ZW). The sex with the same sex chromosomes is called homogametic, with different heterogametic. The female sex is homogametic, and the male sex is heterogametic in some insects (including Drosophila) and all mammals. The reverse ratio is in birds and butterflies. A number of traits in Drosophila are inherited in

in strict accordance with the transfer of X chromosomes to offspring. A female Drosophila showing

a recessive trait, such as white eyes, due to homozygosity for this gene located on the X chromosome, transmits white eyes to all sons, since they receive their X chromosome only from the mother. In the case of heterozygosity for a recessive sex-linked trait, the female passes it on to half of her sons. In opposite sex determination (males XX or ZZ; females XY or ZW), males pass on sex-linked traits to daughters who receive their X(=Z) chromosome from their father. Sometimes, as a result of nondisjunction of sex chromosomes during meiosis, XXY females and XYY males arise. There are also cases of connection of X-chromosomes ends; the females then pass on the linked X chromosomes to their daughters, who display sex-linked traits. Sons are like fathers (such inheritance is called hologenic). If the inherited genes are on the Y chromosome, then the traits determined by them are transmitted only through the male line - from father to son (such inheritance is called hollandic). The chromosome theory of heredity revealed the intracellular mechanisms of heredity, gave an accurate and unified explanation of all the phenomena of inheritance during sexual reproduction, and explained the essence of changes in heredity, that is, variability.

Nonchromosomal theory of heredity . The primary role of the nucleus and chromosomes in heredity does not exclude the transmission of some traits through the cytoplasm, in which structures capable of self-reproduction are found. Units of cytoplasmic (non-chromosomal) heredity differ from chromosomal ones in that they do not diverge during meiosis. Therefore, offspring with non-chromosomal heredity reproduces the signs of only one of the parents (more often the mother). Thus, distinguish nuclear heredity associated with the transmission of hereditary traits located in the chromosomes of the nucleus (sometimes called chromosomal inheritance), and extranuclear heredity, depending on the transfer of self-reproducing structures of the cytoplasm. Nuclear heredity is also realized when vegetative reproduction, but is not accompanied by a redistribution of genes, which is observed during sexual reproduction, but provides a constant transmission of traits from generation to generation, which is only disturbed somatic mutations .

Molecular genetics . The use of new physical and chemical methods, as well as the use of bacteria and viruses as objects of study, dramatically increased the resolution of genetic experiments, led to the study of heredity at the molecular level and the rapid development of molecular genetics. For the first time N.K. Koltsov(1927) put forward and substantiated ideas about the molecular basis of heredity and about the matrix method of reproduction of “hereditary molecules”. In the 40s. 20th century experimentally proven genetic role deoxyribonucleic acids(DNA), and in the 50-60s. its molecular structure has been established and the principles of encoding genetic information have been elucidated. genetic information , embedded in the hereditary structures of organisms (in chromosomes, cytoplasm, cellular organisms), received from ancestors in the form of a set of genes, information about the composition, structure and nature of the metabolism of the substances that make up the body (primarily proteins and nucleic acids) and related functions. In multicellular forms during sexual reproduction, genetic information is transmitted from generation to generation through germ cells - gametes, the only function of which is the transmission and storage of genetic information. Microorganisms and viruses have special types of its transmission. Genetic information is contained mainly in chromosomes, where it is encrypted in a certain linear sequence of nucleotides in deoxyribonucleic acid molecules - DNA (genetic code). Genetic code is a system for encoding hereditary information in nucleic acid molecules, which is implemented in animals, plants, bacteria and viruses in the form of a sequence nucleotides. In natural nucleic acids- deoxyribonucleic (DNA) and ribonucleic (RNA) - there are 5 common types of nucleotides (4 in each nucleic acid), which differ in their nitrogenous base. Bases found in DNA:

adenine(A), guanine(G), cytosine(C), thymine(T); RNA contains uracil (U) instead of thymine. Except them, as a part of nucleinic to - t it is found apprx. 20 rare (so-called non-canonical, or minor) bases, as well as unusual sugars. Since the number of coding characters of the Genetic Code (4) and the number of amino acid varieties in the protein (20) do not match, the code number (i.e., the number of nucleotides encoding 1 amino acid) cannot be equal to 1. Different combinations of 2 nucleotides are possible only 4 2 = 16, but this is also not enough to encrypt all the amino acids. The American scientist G. Gamow proposed (1954) a model of a triplet genetic code, i.e. one in which one amino acid is coded by a group of three nucleotides called a codon. The number of possible triplets is 4 3 = 64, and this is more than three times the number of common amino acids, in connection with which it was suggested that several codons correspond to each amino acid (the so-called degeneracy of the code). Many different models of the genetic code have been proposed, of which three models deserve serious attention (see figure): overlapping code without commas, non-overlapping code without commas, and code with commas. In 1961, F. Crick (Great Britain) with his collaborators confirmed the hypothesis of a triplet non-overlapping code without commas. Installed next. main patterns related to the genetic code: 1) there is a linear correspondence between the nucleotide sequence and the encoded amino acid sequence (collinearity of the genetic code); 2) reading the code starts from a certain point; 3) reading goes in one direction within one gene; 4) the code is non-overlapping; 5) when reading there are no gaps (code without commas); 6) the genetic code, as a rule, is degenerate, i.e. 1 amino acid is encoded by 2 or more synonymous triplets (the degeneracy of the genetic code reduces the likelihood that a mutational substitution of a base in a triplet will lead to an error); 7) the code number is equal to three;

8) the code in wildlife is universal (with some exceptions). The universality of the genetic code is confirmed by experiments on protein synthesis in vitro. If a cell-free system obtained from one organism (for example, Escherichia coli) is supplemented with a nucleic acid matrix obtained from another organism that is far from the first in evolutionary terms (for example, pea seedlings), then protein synthesis will occur in such a system. Thanks to the work of Amer. geneticists M. Nirenberg, S. Ochoa, X. Koran know not only the composition, but also the order of nucleotides in all codons ..

Of the 64 codons in bacteria and phages, 3 codons - UAA, UAG and UGA - do not encode amino acids; they serve as a signal for the release of the polypeptide chain from ribosomes, i.e. signal the completion of the synthesis of the polypeptide. Their name. termination codons. There are also 3 signals about the beginning of synthesis - this is the so-called. initiating columns - AUG, GUG and UUG - to-rye, being included at the beginning of the corresponding messenger RNA (i-RNA), determine the inclusion of formylmethionine in the first position of the synthesized polypeptide chain. The given data are valid for bacterial systems; much is still unclear for higher organisms. Thus, the UGA codon in higher organisms can be significant; the mechanism of polypeptide initiation is also not entirely clear.

The implementation of the genetic code in the cell occurs in two stages. The first of these takes place in the nucleus; he bears the name transcription and consists in the synthesis of mRNA molecules on the corresponding sections of DNA. In this case, the DNA nucleotide sequence is "rewritten" into the RNA nucleotide sequence. The second stage - translation - takes place in the cytoplasm, on ribosomes; in this case, the nucleotide sequence of i-RNA is translated into the sequence of amino acids in the protein; this stage proceeds with the participation of transfer RNA (t-RNA) and the corresponding enzymes.

Genetic information is realized during ontogeny- development of an individual - its transfer from a gene to a trait. All cells of the body arise as a result of divisions of a single source

walking cell - zygotes- and therefore have the same set of genes - potentially the same genetic information. The specificity of cells of different tissues is determined by the fact that different genes are active in them, i.e., not all information is realized, but only part of it, necessary for the functioning of this tissue .

With the study of heredity at the subcellular and molecular level, the idea of ​​the gene was deepened and refined. If in experiments on the inheritance of various traits the gene was postulated as an elementary indivisible unit of heredity, and in the light of cytology data it was considered as an isolated section of the chromosome, then at the molecular level, the gene is a portion of the DNA molecule that is part of the chromosome, capable of self-reproduction and having a specific structure, in which encodes a program for the development of one or more traits of an organism. In the 50s. On microorganisms (American geneticist S. Benzer), it was shown that each gene consists of a number of different sections that can mutate and between which crossing over can occur. Thus, the idea of ​​the complex structure of the gene, which had been developed as far back as the 1930s, was confirmed. A. S. Serebrovsky and N. P. Dubinin based on genetic analysis data.

In 1967-69. the synthesis of viral DNA outside the body was carried out, as well as the chemical synthesis of the yeast alanine transfer RNA gene. A new area of ​​research has become the heredity of somatic cells in the body and in tissue cultures. The possibility of experimental hybridization of somatic cells of different types has been discovered. In connection with the achievements of molecular biology, the phenomena of heredity have become of key importance for understanding a number of biological processes, as well as for many questions of practice.

Heredity and evolution . Even Darwin was clear about the importance of heredity for the evolution of organisms. The establishment of the discrete nature of heredity eliminated

one of the important objections against Darwinism: when crossing individuals that have hereditary changes, the latter should allegedly “dilute” and weaken in their direction. However, in accordance with the laws of Mendel, they are not destroyed and do not mix, but reappear in offspring under certain conditions. In the populations of

The changes in heredity appeared as complex processes based on crosses between individuals, selection, mutations, genetic-automatic processes, etc. This was first pointed out by S.S. Chetverikov(1926), who experimentally proved the accumulation of mutations within a population. I.I. Schmalhausen(1946) put forward a provision on the “mobilization re

ground of hereditary variability “as a material for creative activity natural selection under changing environmental conditions. The significance of different types of changes in heredity in evolution is shown. Evolution is understood as a gradual and repeated change in the heredity of a species. at the same time, heredity, which ensures the constancy of the species organization, is a fundamental property of life associated with the physicochemical structure of the elementary units of the cell, primarily its chromosome apparatus, and which has passed a long period of evolution.

The principles of organization of this structure (genetic code), apparently, are universal for all living beings and are considered as the most important attribute of life.

Ontogenesis is also under the control of heredity, starting with the fertilization of the egg and carried out under specific environmental conditions. Hence the difference between the set of genes received by the body from the parents - genotype and a complex of signs of an organism at all stages of its development - phenotype. The role of the genotype and environment in the formation of the phenotype can be different.

But one should always take into account the genotypically determined norm of the organism's reaction to environmental influences. Changes in the phenotype are not adequately reflected in the genotypic. the structure of germ cells, so the traditional idea of ​​the inheritance of acquired traits is rejected as having no factual. fundamentals and wrong theoretically. The mechanism for the implementation of heredity during the development of an individual, apparently, is associated with a change in the action of different genes over time and is carried out during the interaction of the nucleus and cytoplasm, in which there is a synthesis of certain proteins based on a program recorded in DNA and transmitted to the cytoplasm with messenger RNA.

Patterns of heredity are of great importance for the practice of agriculture and medicine. They are based on the development of new and improvement of existing varieties of plants and animal breeds. The study of the laws of heredity led to the scientific substantiation of the previously used empirical selection methods and to the development of new techniques (experimental mutagenesis , heterosis , polyploidy and etc.).

human genetics is a branch of genetics closely related to anthropology and medicine. Human genetics is conditionally divided into anthropogenetics, which studies the heredity and variability of the normal signs of the human body, and medical genetics, which studies its hereditary pathology (diseases, defects, deformities, etc.). Human genetics is also associated with evolutionary theory, as it explores specific mechanisms of human evolution and its place in nature, with psychology, philosophy, and sociology.Pythogenetics, biochemical genetics, immunogenetics, genetics of higher nervous activity, and physiological genetics are intensively developing in the areas of human genetics.

In human genetics, instead of the classic. hybridological analysis apply genealogical method , to-ry consists in analyzing the distribution in families (more precisely, in pedigrees) of persons who have this trait (or anomaly) and do not have it, which reveals the type of inheritance, the frequency and intensity of the manifestation of the trait, etc. When analyzing family data, one obtains also figures empirical risk, i.e., the probability of possessing a trait depending on the degree of kinship with its carrier. Genealogical the method has already shown that more than 1800 morphological, biochemical. and other signs of a person are inherited according to the laws of Mendel. For example, the dark color of the skin and hair dominates over the light; reduced activity or absence of certain enzymes is determined by recessive genes, and height, weight, intelligence level and a number of other features are determined by “polymeric” genes, i.e., systems from many others. genes. Mn. signs and diseases of a person, inherited sex-linked, are caused by genes localized on the X- or Y-chromosome. Such genes are known approx. 120. These include genes for hemophilia A and B, deficiency of the enzyme glucose-6-phosphate dehydrogenase, color blindness, etc. method of human genetics - twin method. Identical twins (OB) develop from one egg fertilized by one sperm; therefore, the set of genes (genotype) in OBs is identical. Fraternal twins (RB) develop from two or more eggs fertilized by different sperm; therefore, their genotypes differ in the same way as in brothers and sisters.

Heredity and environment .

Genes do not manifest their functions in a vacuum, but in such a highly organized system as a cell, which itself is in a certain environment - among other cells or in the external environment. Whatever the genotype, its properties are manifested only to the extent that environmental conditions allow it.

A plant grown in the dark remains white and feeble; it is unable to extract from carbon dioxide the energy needed for metabolism, even if all its cells contain genetic information. necessary for the development of chloroplasts, as well as the synthesis and activity of chlorophyll. Equally, the genetic potencies that determine the color of the eyes appear only under special conditions that are created in the cells of the iris; these potencies are realized under the condition that the eye itself has developed sufficiently due to the action of numerous genes.

Finally, the phenotype of an organism is the result of interactions between genotype and environment at each this moment his life and at every stage of his individual development.

The actions of the environment can be classified into two types, although in a real situation they are often superimposed on each other. On the one hand, these are strong influences, leading to complete or partial suppression of the expression of genetic potencies, on the other hand, weak influences, expressed only in small changes in the degree of their expression. The first type of influence depends on random circumstances. the second is common and inextricably linked with the functioning of living matter.

The individual development of the higher organism begins with the stage of the zygote. The hereditary potencies he receives from his parents manifest themselves only gradually, in the course of a long and complex process of development. and starting from the first divisions of egg crushing, the environment takes part in their implementation.

For the genes of the future organism, the initial environment is the cytoplasm of the egg, which originates from the mother's organism and embodies cellular continuity. This may be enough to orient the development of the embryo in a direction that does not coincide with its own genotype.

Comparison of intra-pair differences between identical and fraternal twins makes it possible to judge the relative importance of heredity and environment in determining the properties of the human body. In twin studies, the indicator is especially important. concordance, which expresses (in %) the probability of one of the members of the pair of OB or RB having this feature, if another member of the pair has it. If the trait is determined mainly by hereditary factors, then the percentage of concordance is much higher in OB than in RB. For example, concordance for blood types, to-rye are determined only genetically, the OB is 100%. In schizophrenia, concordance in OB reaches 67%, while in RB it is 12.1%; with congenital dementia (oligophrenia) - 94.5% and 42.6%, respectively. Similar comparisons have been made for a number of diseases. Thus, studies of twins show that the contribution of heredity and environment to the development of a wide variety of traits is different and traits develop as a result of the interaction of the genotype and the environment. Some signs are due to preim. genotype, in the formation of other signs, the genotype acts as a predisposing factor (or a factor that limits the rate of the body's reaction to the actions of the external environment).

Diseases associated with mutations . Genome human includes several million genes that can also affect the development of traits in different ways. As a result of mutations and recombination of genes, diversity inherent in a person arises in a variety of ways. Human genes mutate each at a rate of 1 in 100,000 to 1 in 10,000,000 gametes per generation. Spreading mutations among large population groups, studies human population genetics, which makes it possible to map the distribution of genes that determine the development of normal traits and hereditary diseases. Of particular interest to human population genetics are isolates- groups of the population, in which for some reason (geographical, economic, social, religious, etc.) marriages are concluded more often between members of the group. This leads to an increase in the frequency of consanguinity of those entering into marriage, and hence the likelihood that recessive genes will go into a homozygous state and manifest themselves, which is especially noticeable when the isolate is small.

Research in the field of human genetics has demonstrated the presence of natural selection in human populations. However, selection in humans acquires specific features: it acts intensively only at the embryonic stage (for example, spontaneous abortions are a reflection of such selection). Selection in human society is carried out through differential marriage and fertility, that is, as a result of the interaction of social and biological factors. The mutation process and selection cause a huge

diversity (polymorphism) in a number of ways, inherent in man, which makes him a biological. point of view with an unusually plastic and adapted look.

The widespread use of cytological methods in human genetics contributed to the development cytogenetics, where the main object of study is chromosomes, i.e., structures of the cell nucleus, in which genes are localized. It was established (1946) that the chromosome set in the cells of the human body (somatic) consists of 46 chromosomes, and the female sex is determined by the presence of two X chromosomes, and the male sex is determined by the presence of an X chromosome and a Y chromosome. Mature germ cells contain half (haploid) number of chromosomes. Mitosis, meiosis And fertilization maintain the continuity and constancy of the chromosome set both in a series of cell generations and in generations of organisms. As a result of violations of these processes, anomalies of the chromosome set can occur with a change in the number and structure of chromosomes, which leads to the occurrence of chromosomal diseases, which are often expressed in dementia, the development of severe congenital deformities, anomalies of sexual differentiation, or cause spontaneous abortions.

The history of the study of chromosomal diseases originates from clinical studies conducted long before the description of human chromosomes and the discovery of chromosomal abnormalities.

Chromosomal diseases - Down's disease, syndromes: Turner, Klinefelter, Patau, Edwards.

With the development of the autoradiography method, it became possible to identify some individual chromosomes, which contributed to the discovery of a group of chromosomal diseases associated with structural rearrangements of chromosomes. The intensive development of the theory of chromosomal diseases began in the 70s of the 20th century. after the development of methods for differential staining of chromosomes.

The classification of chromosomal diseases is based on the types of mutations of the chromosomes involved. Mutations in germ cells lead to the development of complete forms of chromosomal diseases, in which all cells of the body have the same chromosomal abnormality.

Currently, 2 variants of violations of the number of chromosome sets have been described - tetraploidy And triplodia. Another group of syndromes is caused by violations of the number of individual chromosomes - trisomy(when there is an extra chromosome in the diploid set) or

monosomy(one of the chromosomes is missing). Monosomy autosomes are incompatible with life. Trisomy is a more common pathology in humans. A number of chromosomal diseases are associated with a violation of the number of sex chromosomes.

The most numerous group of chromosomal diseases are syndromes caused by structural rearrangements of chromosomes. Allocate chromosomal syndromes of the so-called

partial monosomy (increase or decrease in the number of individual chromosomes not on the whole chromosome, but on its part).

Due to the fact that the vast majority of chromosomal anomalies belong to the category of lethal mutations, 2 indicators are used to characterize their quantitative parameters - the frequency of distribution and the frequency of occurrence. It was found that about 170 out of 1000 embryos and fetuses die before birth, of which about 40% - due to the influence of chromosomal disorders. Nevertheless, a significant part of mutants (carriers of a chromosomal anomaly) bypasses the effect of intrauterine selection.

But some of them die at an early age, before reaching puberty. Patients with anomalies of the sex chromosomes due to violations of sexual development, as a rule, do not leave offspring. Hence, all anomalies can be attributed to mutations. It has been shown that, in the general case, chromosomal mutations almost completely disappear from the population after 15–17 generations.

For all forms of chromosomal diseases, a common feature is the multiplicity of disorders (congenital malformations). Common manifestations of chromosomal diseases are: delayed physical and psychomotor development, mental retardation, musculoskeletal anomalies, defects in the cardiovascular, genitourinary, nervous and other systems, deviations in the hormonal, biochemical and immunological status, etc.

The degree of organ damage in chromosomal diseases depends on many factors - the type of chromosomal abnormality, missing or excess material of an individual chromosome, the genotype of the organism, and the environmental conditions in which the organism develops.

The etiological treatment of chromosomal diseases has not yet been developed.

The development of methods for prenatal diagnosis makes this approach effective in combating not only chromosomal but also other hereditary diseases.

Treatment and prevention of hereditary diseases. Advances in human genetics have made prevention and treatment possible hereditary diseases. One of effective methods their warnings - medical genetic counseling with a prediction of the risk of the appearance of the disease in the offspring of persons suffering from this disease or having a sick relative. Achievements in human biochemical genetics have revealed the root cause (molecular mechanism) of many hereditary defects, metabolic anomalies, which contributed to the development of express diagnostic methods that allow for rapid and early detection of patients, and treatment of many others. previously incurable inheritances, diseases. Most often, treatment consists in the introduction into the body of substances that are not formed in it due to a genetic defect, or in the preparation of special diets, from which substances that have a toxic effect on the body as a result of a hereditary inability to split them are eliminated. Many genetic defects are corrected with the help of timely surgical intervention or pedagogical correction. Practical measures aimed at maintaining the hereditary health of a person, at protecting gene pool humanity, are carried out through the system medical genetic consultations. The main goal of medical genetic counseling is to inform interested parties about the likelihood of the risk of the appearance of patients in the offspring. Propaganda of genetic knowledge among the population also belongs to medical genetic measures, since this contributes to a more responsible approach to childbearing. Medical genetic counseling refrains from coercive or encouraging measures in matters of childbearing or marriage, assuming only the function of information. Of great importance is the system of measures aimed at creating the best conditions for the manifestation of positive, inheritances, inclinations and the prevention of the harmful effects of the environment on human heredity.

Human genetics is the natural scientific basis for the fight against racism convincingly showing that race- these are forms of human adaptation to specific environmental conditions (climatic and other), that they differ from each other not in the presence of "good" or "bad" genes, but in the frequency of distribution of ordinary genes characteristic of all races. Human genetics shows that all races are equal (but not the same) from a biological point of view.

vision and have equal opportunities for development, determined not by genetic but by socio-historical conditions. Statement of biological hereditary differences

between individuals or races cannot serve as the basis for any conclusions of a moral, legal or social order that infringe on the rights of these people or races. The data of human genetics have shown that the genes that determine the development of various deformities and hereditary diseases are quite frequent: hereditary metabolic diseases, mental illnesses, etc. medical genetic consultations. Early diagnosis of hereditary diseases allows you to apply the necessary methods of treatment. It is essential to take into account heredity in the reaction different people medicines and other chemicals, and

in immunology, reactions. The role of molecular genetic mechanisms in the etiology of malignant tumors is indisputable.

The phenomena of heredity appear in different forms depending on the level of life at which they are studied (molecule, cell, organism, population). But ultimately, heredity is ensured by the self-reproduction of the material units of heredity (genes and cytoplasmic elements), the molecular structure of which is known. The natural matrix nature of their autoreproduction is also disturbed by mutations in individual genes or rearrangements of genetic systems as a whole. Any change in a self-reproducing element is inherited constly.

genetic engineering.

What is genetic engineering ? genetic engineering- This is a branch of molecular genetics associated with the targeted creation of new combinations of genetic material. The basis of applied genetic engineering is the theory of the gene. The created genetic material is capable of reproducing in the host cell and synthesizing end products of metabolism.

From the history of genetic engineering . Genetic engineering originated in 1972 at Stanford University in the USA. Then the laboratory of P. Berg received the first recombinant (hybrid) DNA or (recDNA). It combined DNA fragments of the lambda phage, Escherichia coli and the monkey virus SV40.

The structure of recombinant DNA . Hybrid DNA has the form of a ring. It contains a gene (or genes) and a vector. A vector is a DNA fragment that ensures the reproduction of hybrid DNA and the synthesis of end products of the genetic system - proteins. Most of the vectors were obtained on the basis of the lambda phage, from plasmids, SV40 viruses, polyoma, yeast, and other bacteria. Protein synthesis occurs in the host cell. Most often, E. coli is used as a host cell, but other bacteria, yeasts, and animals are also used.

or plant cells. The host-vector system cannot be arbitrary: the vector is tailored to the host cell. The choice of vector depends on the species specificity and the objectives of the study. Two enzymes are of key importance in the construction of hybrid DNA. The first - restriction enzyme - cuts the DNA molecule into fragments in strictly defined places. And the second - DNA ligases - sew DNA fragments into a single whole. Only after the isolation of such enzymes did the creation of artificial genetic structures become a technically feasible task.

Stages of gene synthesis . The genes to be cloned can be obtained as fragments by mechanical or restrictase fragmentation of total DNA. But structural genes, as a rule, have to be either synthesized chemically and biologically or obtained in the form of a DNA copy of messenger RNA corresponding to the chosen gene. Structural genes contain only an encoded record of the final product (protein, RNA), and are completely devoid of regulatory regions. And therefore they are not able to function in the host cell.

Upon receipt of recDNA, several structures are most often formed, of which only one is necessary. Therefore, the mandatory step is the selection and molecular cloning of recDNA introduced by transformation into the host cell. There are 3 ways of recDNA selection: genetic, immunochemical and hybridization with labeled DNA and RNA.

Practical results of genetic engineering. As a result of the intensive development of genetic engineering methods, clones of many genes of ribosomal, transport and 5S RNA, histones, mouse, rabbit, human globin, collagen, ovalbumin, human insulin and other peptide hormones, human interferon, etc. have been obtained. This made it possible to create strains of bacteria that produce many biologically active substances used in medicine, agriculture and the microbiological industry.

On the basis of genetic engineering, a branch of the pharmaceutical industry called the “DNA industry” arose. This is one of the modern branches of biotechnology.

Human insulin (humulin) obtained by means of recDNA is approved for therapeutic use. In addition, based on numerous mutants for individual genes obtained during their study, highly effective test systems have been created to detect the genetic activity of environmental factors, including the detection of carcinogenic compounds.

Theoretical significance of genetic engineering. In a short time, genetic engineering has had a huge impact on the development of molecular genetic methods and has made it possible to make significant progress along the path of understanding the structure and functioning of the genetic apparatus. Genetic engineering has great prospects in the treatment of hereditary diseases, of which about 2000 have been registered to date. designed to help correct the mistakes of nature.

Great strides have been made in cloning . Clone, or group of cells, is formed by the division of the first cell. Each human somatic cell carries the same set of genes, the entire

hereditary information. If it starts to divide, then a new organism will grow. with the same genotype. IN 1997 g. doctor Jan Wilmuth in Scotland in Eddinburgh received with a group of scientists lamb dolly(artificially). This lamb does not have a father, as the cage was taken from the mother. There was a fear that genetic engineering experiments could be dangerous for humanity. IN 1974 g. spec. The Commission of American Biologists has published a message to the world's geneticists recommending against experimenting with certain types of DNA until safety measures are developed.

But still it was necessary to develop restrictive measures. July 30, 1997 The science committee in the US Congress voted to completely ban human cloning experiments. The President had previously banned the allocation of money for these experiments.

In Russia in 1996 The State Duma adopted a law on state regulation in the field of gene. engineering.

Personality genes .

“ One of the miracles that we observe daily and hourly is the unique individuality of every person living on Earth. Scientists for a long time could not find the key to this riddle.

It is known that all information about the structure and development of a living organism is “recorded” in its genome - a set of genes. It is believed that genomic differences within one species are very insignificant.” For example, the human eye color gene differs from the rabbit eye color gene, but in different people this gene is arranged in the same way and consists of the same DNA sequences.

There is a huge variety of proteins from which they are built living organisms and an amazing variety of genes encoding these proteins. In the genome of each person there are some areas that determine his personality. Some human genes differ from rat genes by only a few nucleotides, which are signs of the genetic code. Other genes are different, but the same in two people. The variability associated with the existence of genes similar to those of the human blood type does not explain the enormous diversity of natural proteins either.

In 1985, special ultra-variable mini-satellite regions were discovered in the human genome. These sections of DNA turned out to be individual for each person and with their help it was possible to obtain a “portrait” of his DNA. e. certain genes.

This “portrait” is a complex combination of dark and light stripes, similar to a slightly blurred spectrum, or a keyboard of dark and light keys of different thicknesses. This combination is called DNA fingerprints (similar to fingerprints) or “DNA profile”

“Special markers, or DNA probes, have been constructed based on highly variable DNA sequences.” Markers labeled with a radioactive isotope are added to DNA processed in a special way, with which the former find similar hypervariable regions on the DNA and attach to them. These areas become radioactive, so that they can be detected by autoradiography. Each person has a distribution of such

places individually. Where the markers are attached to a large number hypervariable areas on DNA (many radioautographic signals) - this is a wide dark band. Where there are few places of attachment, there is a narrow dark strip. Where there are none at all, there is a bright stripe.

So, scientists have discovered that the human genome is literally “saturated” with super-variable DNA sequences. Previously elusive individual DNA sequences began to be detected.

After unraveling the individuality of man, the question arose: do other organisms have the same individuality? Do they have hypervariable DNA sequences? Scientists had to find a universal marker that is equally suitable for both bacteria and humans. It turned out to be bacteriophage(bacteria virus). This discovery was extremely important for the work of geneticists and breeders.

It turned out that with the help of DNA fingerprints it is possible to carry out identification of a person much more successfully than traditional methods of fingerprinting and blood tests allowed. The probability of error is one in several million. The new discovery was immediately taken advantage of by criminologists, who quickly and effectively put it into practice.

With the help of DNA fingerprints, it is possible to investigate crimes not only of the present, but also of the deep past.

“Genetic examinations to establish paternity are the most frequent reason for judicial authorities to turn to genetic fingerprinting. Men who doubt their paternity and women who wish to obtain a divorce on the basis of

that their husband is not the father of the child. Motherhood can be identified by DNA prints of the mother and child in the absence of the father, and vice versa. DNA fingerprints of the father and child are sufficient to establish paternity. In the presence of the material of the mother, father and child, DNA prints look no more complicated than a picture from a school textbook: each stripe on the DNA print of a child can be “addressed” to either the father or the mother.”

The most interesting are the applied aspects of genetic fingerprinting. The question arises of certification of DNA prints of recidivist criminals, the introduction of data on DNA prints along with a description of appearance into the file cabinets of the investigating authorities. special signs, fingerprints.

Conclusion

Everything we know today about the mechanisms of heredity operating at all levels of organization of the living (individual, cell, subcellular structure, molecule) has been established thanks to the theoretical and technical contributions of many disciplines - biochemistry, crystallography, physiology, bacteriology, virology, cytology... and finally genetics. In this cooperation, genetics acted as the leading principle of research, unifying the results obtained. The genetic interpretation of biological phenomena is essentially of a unifying significance, as is well expressed in the already classic afforism of J. Monod: “Everything that is true for a bacterium is true for an elephant.” On present stage biological knowledge, it is quite reasonable to believe that all the properties of organisms, including humans, can be fully explained (if not already explained) by the characteristics of their genes and the proteins that they encode. Therefore, no matter what branch of biology the phenomenon under study belongs to, be it embryology, physiology, pathology or immunology. it is no longer possible to ignore its genetic basis. Behind each phenomenon lies its strict determination - a group of working genes and proteins that perform their functions.

These facts together represent a solid contribution of genetics to the understanding of the primary mechanisms of life. But the significance of genetics does not end there. it is also connected with the internal features of the genetic method.

The geneticist deals with mutations, which serve as his working material. Indeed, a mutation. expressed in a hereditary change of some property, reveals a certain proportion of the genetic material of the organism, the existence and function of which would otherwise be difficult to guess. Genetic analysis (consisting in tracing the transmission of a trait during sexual reproduction) allows you to determine the number of genes responsible for the trait under study. and their localization. If the sign is an empirical fact, complex (since it corresponds to the external expressions of the complex interaction of elementary phenomena) and, moreover, changing depending on the conditions of the environment and

numerous microfactors eluding the experimenter's control. then the gene, on the contrary, is an exact, concrete, and stable fact. Absolutely obvious. that the desire to decompose a given phenomenon into its genetic components always contributes to the formation of a method of clear logical analysis.

In addition, the use of genetic data is the only method that allows a biologist to conduct a strictly scientific pilot study and compare the results with confidence. Thus, genetics provides us with both a theoretically rational approach, which brings clarity to the understanding of the phenomena under study, and an accurate experimental method. They will certainly retain their value until then. until all the properties of living organisms are satisfactorily explained.

Terminological dictionary

Allelic genes- genes located at the same points on homologous chromosomes. An allele can be dominant and recessive.

haploidy- the state of a cell with a half chromosome set (there is only one of the two homologous chromosomes). The haploid set of chromosomes is possessed by female and male germ cells.

genetic recombination- exchange of sections of genetic material between homologous chromosomes or chromatids in the process of cell division.

Genome- a set of genes contained in a haploid set of chromosomes.

Genotype- the totality of genes in the genetic set of a given species.

Heterozygosity- the state of the hybrid genetic set, in which homologous chromosomes contain different alleles.

Heterochromatin- Spiralized, intensely stained sections of chromosomes that have a peculiar genetic function.

hyperploidy- the presence of more than usual, the amount of genetic material.

hypoploidy- the presence in the cells of a smaller than normal amount of genetic material.

Homozygosity- the state of the genetic set, in which paired genes on homologous chromosomes are the same.

homologous chromosomes- chromosomes that are similar in structure and carry the same set of allelic genes.

Diploidy- the presence of an even number of chromosomes in cells, in which each chromosome corresponds to its homologue.

Cell differentiation- the process of specialization of the functions and biochemical properties of cells in the body.

DNA- deoxyribonucleic acid - a chemical compound that encodes genetic information and stores it in the chromosomes of eukaryotic cells.

dominance- the predominant appearance in the phenotype of one of two paired genetic traits, as opposed to a recessive trait.

Chromosomal conjugation- temporary connection of homologous chromosomes.

Meiosis- a special type of cell division. Its biological meaning is genetic recombination and the appearance of haploid germ cells.

Membrane- in biology, a designation for protein-lipid cell membranes and intracellular partitions.

Mitosis- a set of complex processes during the division of non-sex cells.

Mitochondria- particles in the cytoplasm of the cell that produce energy for its life.

Mutation- random change in genetic material. inherited.

sex chromosomes- Humans have X and Y chromosomes. All the rest (a person has 22 pairs) are called autosomes.

protokaryotic cells- cells in which DNA is not contained in a clearly defined nucleus.

DNA replication- duplication of the DNA molecule before cell division.

recessiveness- lack of manifestation of this allele in a pair with a dominant allele.

Ribosomes- particles in the cell, consisting of RNA and protein. Ribosomes read (translate) messenger RNA and form proteins.

RNA- ribonucleic acid - a chemical compound, a product of the genetic activity of DNA. Serves to carry genetic messages within cells.

somatic cells- any cells of the body, except for the sex cells.

Phenotype- a set of properties and characteristics of an organism. which are the results of the interaction of the genotype of the individual and the environment.

Enzyme a protein that catalyzes certain chemical reactions in a cage. The amino acid sequence in it is determined by the corresponding gene or genes.

Chromosomes- the main structural part of the cell nucleus, containing DNA and protein.

Chromatids Chromosomes that have undergone the process of doubling during cell division.

Cistron- one of the equivalents of the concept of "gene".

Cytoplasm The part of the cell that surrounds the cell nucleus. It is in the cytoplasm that protein synthesis occurs on ribosomes.

eukaryotic cells- cells. having a nucleus. limited from the cytoplasm.

Euchromatin- despiralized, genetically active sections of DNA in the nuclei of cells.

nucleolus- structure inside the cell nucleus. Site of ribosomal RNA synthesis.

Bibliography:

1.C. H. Karpenkov “Concepts of modern natural science”, M., 1997

2. V. A. Orekhova, T. A. Lashkovskaya, M. P. Sheybak “Medical genetics”, Minsk, 1997

3. A. A. Bogdanov, B. M. Mednikov “Power over the gene”, Moscow “Enlightenment”, 1989

4. A. A. Kamensky, N. A. Sokolova, S. A. Titov “Biology”, Moscow, 1997

5. Biological encyclopedic Dictionary, Moscow, 1989

6. Maniatis T., Methods of genetic engineering, M., 1984 ;

A. A. Bogdanov, B. M. Mednikov “Power over the gene”, Moscow “Enlightenment”, 1989, p. 3.

V. A. Orekhova, T. A. Lashkovskaya, M. P. Sheybak “Medical genetics”, Minsk, 1997, p. 4.

Kamensky A. A., Sokolova N. A., Titov S. A. “Biology”, Moscow, 1997, p. 60.

V. A. Orekhova, T. A. Lashkovskaya, M. P. Sheybak “Medical genetics”, Minsk, 1997, p. 49.

S. Kh. Karpenkov ‘Concepts of modern natural sciences’, M., 1997, p. 309.

S. Kh. Karpenkov “Fundamentals of modern natural science”, M., 1997, p. 309.

S. Kh. Karpenkov “Fundamentals of modern natural science”, M., 1997, p. 311.