1) i-RNA 2) t-RNA 3) DNA 4) chromosome

A2. In the daughter cells of human skin during their reproduction comes from the mother cell:

complete genetic information

half of the information

a quarter of information

no right answer

A3. DNA replication is accompanied by the breaking of chemical bonds:

peptide, between amino acids

covalent, between carbohydrate and phosphate

hydrogen, between nitrogenous bases

ionic, inside the structure of the molecule

A4. During the replication of a DNA molecule, the following is formed:

a thread that has broken into separate fragments of daughter molecules

a molecule made up of two new strands of DNA

a molecule half of which consists of a strand of mRNA

daughter molecule consisting of one old and one new strand of DNA

A5. Transcription is a process:

1) DNA replication

2) i-RNA synthesis

3) protein synthesis

4) attachment of t-RNA to an amino acid

A6. If an amino acid is encoded by the codon UGG, then in DNA it corresponds to a triplet:

TCC 2) AGG 3) UCC 4) ACC

A7. One DNA triplet carries information about:

Amino acid sequences in a protein molecule

The location of a specific AA in a protein chain

Sign of a particular organism

Amino acid included in the protein chain

A8. The number of tRNAs involved in translation is equal to the number of:

i-RNA codons that code for amino acids

Molecule i-RNA

The genes that make up the DNA molecule

Proteins synthesized on ribosomes

A9. The period of a cell's life from division to division is called:

Interphase 3) meiosis

Mitosis 4) cell cycle

A10. How many chromatids are contained in 8 chromosomes visible in the metaphase of mitosis:

1) 6 2) 8 3) 12 4) 16

A11. The number of chromosomes in human somatic cells after mitosis is:

1) 23 2) 46 3) 92 4) 44

Each protein is represented by one or more polypeptide chains. A section of DNA that carries information about one polypeptide chain is called a gene. Each DNA molecule contains many different genes. The totality of DNA molecules in a cell acts as a carrier of genetic information. Due to the unique property - the ability to duplicate, which no other known molecule has, DNA can be copied. When dividing, "copies" of DNA diverge into two daughter cells, each of which, as a result, will have the same information that was contained in the mother cell. Since genes are sections of DNA molecules, two cells formed during division have the same sets of genes. Each cell of a multicellular organism during sexual reproduction arises from one fertilized egg as a result of multiple divisions. This means that a random error in the gene of one cell will be reproduced in the genes of millions of its descendants. That is why all the red blood cells of a patient with sickle cell anemia have the same damaged hemoglobin. The error occurred in the gene that carries information about the beta chain of the protein. A copy of the gene is mRNA. On it, as on a matrix, the wrong protein is "printed" thousands of times in each erythrocyte. Children receive corrupted genes from their parents through their germ cells. Genetic information is passed from one cell to daughter cells, and from parents to children. A gene is a unit of genetic or hereditary information.

Each protein is represented by one or more polypeptide chains. The section of DNA that carries information about one polypeptide chain is called genome. The totality of DNA molecules in a cell acts as a carrier of genetic information. Genetic information is passed on from mother cells to daughter cells and from parents to children. The gene is the unit of genetic, or hereditary information.

DNA is the carrier of genetic information in the cell- does not take a direct part in the synthesis of proteins. In eukaryotic cells, DNA molecules are contained in the chromosomes of the nucleus and are separated by a nuclear membrane from the cytoplasm, where proteins are synthesized. To ribosomes - protein assembly sites - an information carrier is sent from the nucleus, capable of passing through the pores of the nuclear envelope. Messenger RNA (mRNA) is such an intermediary. According to the principle of complementarity, it is synthesized on DNA with the participation of an enzyme called RNA- polymerase.

1) The process of RNA synthesis, in which one of the strands of the DNA molecule is used as a template, is called transcription .

2) Transcription - this is the mechanism by which the nucleotide sequence of one of the DNA chains is rewritten by the complementary sequence of the mRNA molecule.

Messenger RNA is a single-stranded molecule, and transcription comes from one strand of a double-stranded DNA molecule. It is not a copy of the entire DNA molecule, but only part of it - one gene in eukaryotes or a group of adjacent genes that carry information about the structure of proteins necessary to perform one function in prokaryotes. This group of genes is called operon. At the beginning of each operon is a kind of landing site for RNA polymerase called promoter.this is a specific sequence of DNA nucleotides that the enzyme "recognizes" due to chemical affinity. Only by attaching to the promoter, RNA polymerase is able to start RNA synthesis. Having reached the end of the operon, the enzyme encounters a signal (in the form of a certain sequence of nucleotides) indicating the end of reading. The finished mRNA moves away from DNA and goes to the site of protein synthesis.

There are four stages in the transcription process: 1) RNA binding- polymerase with a promoter; 2) initiation- the beginning of the synthesis. It consists in the formation of the first phosphodiester bond between ATP or GTP and the second nucleotide of the synthesized RNA molecule; 3) elongation– RNA chain growth; those. the sequential addition of nucleotides to each other in the order in which their complementary nucleotides are in the transcribed DNA strand. The elongation rate is 50 nucleotides per second; 4) termination- completion of RNA synthesis.

After passing through the pores of the nuclear membrane, mRNA is sent to the ribosomes, where genetic information is deciphered - it is translated from the "language" of nucleotides to the "language" of amino acids. The synthesis of polypeptide chains according to the mRNA template, which occurs in ribosomes, is called broadcast(lat. translation - translation).

Amino acids, from which proteins are synthesized, are delivered to ribosomes with the help of special RNAs called transport RNAs (tRNAs). There are as many different tRNAs in a cell as there are codons that code for amino acids. At the top of the "sheet" of each tRNA there is a sequence of three nucleotides that are complementary to the nucleotides of the codon in the mRNA. They call her anticodon. A special enzyme - codase - recognizes tRNA and attaches to the "leaf petiole" an amino acid - only the one that is encoded by a triplet complementary to the anticodon. The energy of one ATP molecule is spent on the formation of a covalent bond between tRNA and its “own” amino acid.

In order for an amino acid to be included in the polypeptide chain, it must break away from the tRNA. This becomes possible when the tRNA enters the ribosome and the anticodon recognizes its codon in the mRNA. The ribosome has two sites for binding two tRNA molecules. One of these areas, called acceptor, tRNA enters with an amino acid and attaches to its codon (I). Does this amino acid attach to itself (accept) the growing chain of protein (II)? A peptide bond is formed between them. tRNA, which is now attached together with the mRNA codon in donor section of the ribosome. A new tRNA comes to the vacated acceptor site, bound to the amino acid, which is encrypted by the next codon (III). From the donor site, the detached polypeptide chain is again transferred here and extended by one more link. Amino acids in the growing chain are connected in the sequence in which the codons encoding them are located in the mRNA.

When one of the three triplets is found on the ribosome ( UAA, UAG, UGA), which are "punctuation marks" between genes, no tRNA can take a place in the acceptor site. The fact is that there are no anticodons that are complementary to the nucleotide sequences of "punctuation marks". The detached chain has nothing to attach to in the acceptor site, and it leaves the ribosome. Protein synthesis is complete.

In prokaryotes, protein synthesis begins with the codon AUG, located in the first place in the copy from each gene, occupies such a position in the ribosome that the anticodon of a special tRNA interacts with it, connected with formylmentionine. This modified form of the amino acid methionine immediately enters the donor site and plays the role of a capital letter in the phrase - the synthesis of any polypeptide chain begins with it in the bacterial cell. When the triplet AUG is not in the first place, but inside a copy from the gene, it encodes the amino acid methionine. After completion of the synthesis of the polypeptide chain, formylmethionine is cleaved from it and is absent in the finished protein.

To increase the production of proteins, mRNA often passes simultaneously not one, but several ribosomes. What structure united by one mRNA molecule is called polysome. On each ribosome, identical proteins are synthesized in this bead-like assembly line.

Amino acids are continuously supplied to ribosomes by tRNA. Having donated the amino acid, the tRNA leaves the ribosome and is connected with the help of a codase. The high coherence of all the "services of the plant" for the production of proteins allows, within a few seconds, to synthesize polypeptide chains consisting of hundreds of amino acids.

Properties of the genetic code. Through the process of transcription in a cell, information is transferred from DNA to protein.

DNA → mRNA → protein

The genetic information contained in DNA and mRNA is contained in the sequence of nucleotides in molecules.

How does the translation of information from the "language" of nucleotides into the "language" of amino acids take place? This translation is carried out using the genetic code. code or cipher, is a system of symbols for translating one form of information into another. Genetic code is a system for recording information about the sequence of amino acids in proteins using the sequence of nucleotides in mRNA.

What are the properties of the genetic code?

1. triplet code. RNA contains four nucleotides: A, G, C, W. If we tried to designate one amino acid with one nucleotide, then 16 out of 20 amino acids would remain unencrypted. A two-letter code would encrypt 16 amino acids. Nature has created a three-letter, or triplet, code. It means that each of the 20 amino acids is coded for by a sequence of three nucleotides called a triplet or codon.

2. The code is degenerate. It means that each amino acid is encoded by more than one codon. Exceptions: meteonine and tryptophan, each of which is encoded by one triplet.

3. The code is unambiguous. Each codon codes for only one amino acid.

4. There are "punctuation marks" between genes. In printed text, there is a period at the end of each phrase. Several related phrases make up a paragraph. In the language of genetic information, such a paragraph is an operon and its complementary mRNA. Each gene in the prokaryotic operon or an individual eukaryotic gene encodes one polypeptide chain - a phrase. Since in some cases several different polypeptide chains are sequentially created on the mRNA template, they must be separated from each other. For this, there are three special triplets in the genetic year - UAA, UAG, UGA, each of which indicates the cessation of the synthesis of one polypeptide chain. Thus, these triplets perform the function of punctuation marks. They are at the end of every gene.

5. There are no "punctuation marks" within the gene.

6. The code is universal. The genetic code is the same for all creatures living on Earth. In bacteria and fungi, wheat and cotton, fish and worms, frogs and humans, the same triplets encode the same amino acids.

Principles of DNA replication. The continuity of genetic material in the generations of cells and organisms is ensured by the process replication - duplication of DNA molecules. This complex process is carried out by a complex of several enzymes and proteins that do not have catalytic activity, which are necessary to give polynucleotide chains the desired conformation. As a result of replication, two identical double helixes of DNA are formed. These so-called daughter molecules are no different from each other and from the original parent DNA molecule. Replication occurs in the cell before division, so each daughter cell receives exactly the same DNA molecules that the mother cell had. The replication process is based on a number of principles:

1. complementarity. Each of the two strands of the parent DNA molecule serves as a template for the synthesis of its complementary, i.e. complementary, daughter chain.

2. semi-conservative. As a result of replication, two daughter double strands are formed, each of which preserves (preserves) one of the parent DNA strands unchanged. The second chains of daughter molecules are re-synthesized from nucleotides along the trailer of complementarity to the parent DNA strands. Daughter DNA is no different from each other and from the parent double helix.

3.
anti-parallelism. Each strand of DNA has a specific orientation. One end carries a hydroxyl group (-OH) attached to the 3'-carbon in the sugar deoxyribose, at the other end of the chain is a phosphoric acid residue at the 5'-position of the sugar. Two complementary strands in a DNA molecule are oriented in opposite directions - antiparallel. Enzymes that synthesize new DNA strands and are called DNA polymerases can move along the template strands in only one direction - from their 3'-ends to 5'-ends. In this case, the synthesis of complementary strands is always carried out in the 5'→3' direction, i.e. unipolar. Therefore, in the process of replication, the simultaneous synthesis of new chains proceeds antiparallel.

4. Discontinuity. In order for new DNA strands to be built according to the principle of complementarity, the double helix must be untwisted and there must be no hydrogen bonds between the parent strands.

Only in this case, DNA polymerases are able to move along the parent strands and use them as templates for the error-free synthesis of daughter strands. But the complete unwinding of helices, consisting of many millions of base pairs, is associated with such a significant number of rotations and such energy costs that are impossible under cell conditions. Therefore, replication in eukaryotes begins simultaneously in some places of the DNA molecule. The region between two points where the synthesis of daughter chains begins is called replicon. He is unit of replication.

Each DNA molecule in a eukaryotic cell contains many replicons. In each replicon, one can see a replication fork - that part of the DNA molecule that has already unraveled under the action of special enzymes. Each strand in the fork serves as a template for the synthesis of a complementary daughter strand. During replication, the fork moves along the parent molecule, while new sections of DNA are untwisted. Since DNA polymerases can move only in one direction along the matrix strands, and the strands are oriented antiparallel, two different enzymatic complexes simultaneously synthesize in each fork. Moreover, in each fork, one daughter (leading) chain grows continuously, and the other (lagging) chain is synthesized by separate fragments several nucleotides long. Such enzymes, named after the Japanese scientist who discovered them fragments of Okazaki are linked by DNA ligase to form a continuous chain. The mechanism of formation of daughter chains of DNA fragments is called discontinuous.

5. Need for primer DNA polymerase is not able to start the synthesis of the leading strand, nor the synthesis of the Okazaki fragments of the lagging strand. It can only build up an already existing polynucleotide strand by sequentially attaching deoxyribonucleotides to its 3'-OH end. Where does the initial 5' end of the growing DNA strand come from? It is synthesized on the DNA template by a special RNA polymerase called primase(English Primer - seed). The size of the ribonucleotide primer is small (less than 20 nucleotides) in comparison with the size of the DNA chain formed by DNA poimerase. Fulfilled his Functions The RNA primer is removed by a special enzyme, and the gap formed during this is closed by DNA polymerase, which uses the 3'-OH end of the neighboring Okazaki fragment as a primer.

The problem of underreplication of the ends of linear DNA molecules. Removal of the outermost RNA primers that are complementary to the 3' ends of both strands of the linear parent DNA molecule results in the daughter strands being shorter than 10–20 nucleotides. This is the problem of underreplication of the ends of linear molecules.

The problem of underreplication of the 3' ends of linear DNA molecules is solved by eukaryotic cells using a special enzyme - telomerase.

Telomerase is a DNA polymerase that completes the 3'-terminal DNA molecules of chromosomes with short repeating sequences. They, located one after another, form a regular terminal structure up to 10 thousand nucleotides long. In addition to the protein part, telomerase contains RNA, which acts as a template for extending DNA with repeats.

Scheme of elongation of the ends of DNA molecules. First, complementary binding of the protruding DNA end to the template site of telomerase RNA occurs, then telomerase builds up DNA using its 3'-OH end as a seed, and RNA, which is part of the enzyme, as a template. This stage is called elongation. After that, translocation occurs, i.e. movement of DNA, extended by one repeat, relative to the enzyme. This is followed by elongation and another translocation.

As a result, specialized end structures of chromosomes are formed. They consist of repeatedly repeated short DNA sequences and specific proteins.

Brief summary.

Lesson in general biology.

Topic: “DNA is a carrier of hereditary information.

Genetic code".

The purpose of the lesson : to consolidate knowledge about the structure of DNA and RNA, to study the concept of a gene, the genetic code, its properties.

Equipment: table “Structure of an animal cell”, “Proteins”, DNA model, multimedia installation,presentation in power point.

During the classes

1. Org. moment …………………………………………………………………… 1-2 min.

2. Main part: …………………………………………………………….... 30 min.

2.1 Repetition of the previously studied: ………………………………………….…. 12 min

2.2 Learning new material: ……………………………….………………… 18 min

3. Fixing …………………………………………………………………….8 min

2.1. Repetition of previously learned

Questions for students:

1. What are proteins?
2. What are the monomers of all natural proteins? (20 amino acids).
3. What are the functions of proteins? (Name the structural features of nucleic acids)
4. Remember where DNA molecules are found in plant and animal cells?
5. What is complementarity?
6. Name the types of RNA.

2.2. Learning new material

All properties of any organism are determined by its protein composition. Moreover, the structure of each protein is determined by the sequence of amino acid residues. Consequently, as a result, hereditary information, which is transmitted from generation to generation, should contain information about the primary structure of proteins.

genetic information- this is information about the structure of all proteins of the body enclosed in DNA molecules.

Gene - This is a section of a DNA molecule that encodes the primary structure of one polypeptide chain. DNA contains information about the primary structure of a protein.

Genetic code- a set of combinations of three nucleotides encoding 20 types of amino acids that make up proteins.

Properties of the genetic code:

• triplet code. Each AA (amino acid) corresponds to a section of the DNA chain, and, accordingly, an mRNA of three adjacent nucleotides. At present, the genetic code has been completely deciphered and a map has been compiled, that is, it is known which triplets correspond to one or another amino acid out of 20 that make up proteins.
• The code is unambiguous. Each codon codes for only one AK.
• The code is redundant (specific). This means that each AA is coded for by more than one codon (with the exception of methionine and tryptophan). DNA consists of 4 different types of nucleotides, and the smallest structural unit of a gene is a triplet of nucleotides. Therefore, the number of possible combinations is 43 = 64. There are only 20 different amino acids. Thus, there are more than enough different triplets of nucleotides to encode all amino acids.
• The code does not overlap. Any nucleotide can be part of only one triplet.
• There are “punctuation marks” between genes. Of the 64 triplets - U-A-A, U-A-G, U-G-A do not encode AK (consider the table of the genetic code in the textbook). These triplets are signals for the end of polypeptide chain synthesis. The need for these triplets is explained by the fact that in some cases several polypeptide chains are synthesized on mRNA, and these triplets are used to separate them from each other.
• The code is universal. The genetic code is the same for all living organisms living on Earth.

3. Fixing:

Do the exercises in the workbook. (Workbook for textbooks Zakharova V.B., Sukhova T.S. and etc.)

Homework.§ 2.10 p. 73–75, textbook by V. B. Zakharov, S. G. Mamontov, N. I. Sonina, E. T. Zakharova Grade 10 “Biology. General biology”, lesson summary.

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Topic: “DNA is a carrier of hereditary information. Genetic code"

Structural Catalytic (B-enzymes) Regulatory (B-hormones) Contractile Transport Protective Reserve Energy Function

The structure of NK RNA ________________________________ DNA Nitrogenous base (A, G, C, U) FA residue Carbohydrate - ribose Nitrogenous Base (A, G, C, T) Carbohydrate - deoxyribose FA residue

In the chromosomes of the nucleus

Complementarity is the spatial complementarity of molecules or their parts, leading to the formation of hydrogen bonds. Complementary structures fit together like a “key with a lock” (A + T) + (G + C) \u003d 100%

Genetic information is information about the structure of all body proteins contained in DNA molecules 1 gene \u003d 1 protein molecule

Types of RNA There are several types of RNA in the cell. All of them are involved in protein synthesis. Transfer RNAs (tRNAs) are the smallest RNAs. They bind AA and transport them to the site of protein synthesis. Messenger RNA (i-RNA) - they are 10 times larger than tRNA. Their function is to carry information about protein structure from DNA to the site of protein synthesis. Ribosomal RNA (rRNA) - have the largest molecular size, are part of the ribosomes.

A gene is a section of a DNA molecule that encodes the primary structure of one polypeptide chain. The genetic code is a set of combinations of three nucleotides encoding 20 types of amino acids that make up proteins.

One amino acid is coded for by three nucleotides (one codon). ACT ACC GAT Triplet, codon gene AK1 AK2 AK3 protein Properties of the genetic code: Code triplet. Each AK corresponds to a section of the DNA chain, and, accordingly, to an mRNA of three adjacent nucleotides.

The code is unambiguous. Each codon codes for only one AK. The code is redundant. This means that each AA is coded for by more than one codon (with the exception of methionine and tryptophan). The code is non-overlapping. Any nucleotide can be part of only one triplet. There are "punctuation marks" (polarity) between genes. Of the 64 triplets - U-A-A, U-A-G, U-G-A do not encode AK. The code is universal. The genetic code is the same for all living organisms living on Earth.

Homework Lesson summary Prepare a message: "The genetic code."

Problem solving 1) Using the table of the DNA genetic code, determine which AAs are encoded by triplets: CAT, TTT, GAT. 2) Using the table of the genetic code, draw a section of DNA that encodes information about the following sequence of amino acids in a protein: - alanine - arginine - valine - glycine - lysine.

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 deservedly received 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, they distinguish: 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 lost, 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.