DNA carrier of hereditary information. Lesson

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A and RNA
B T RNA
In DNA
Hromosomes

The basis of individuality, the specificity of the organisms lies:
And the structure of organism proteins
B The structure of cells
In cell function
G The structure of amino acids

DNA carries information about the structure
And proteins, fats, carbohydrates
B proteins and fats
In amino acids
G protekov

In one gene encoded information:
And about the structure of several proteins
B about the structure of one of the chains of DNA
In the primary structure of one protein molecule
G about the structure of amino acids

Which nucleotide is not part of DNA?
And Timin
Buracil
In Guanin
G Citozin
D Adenin

What connections are broken into the DNA molecule when doubling it?
And peptide
B covalent, between carbohydrate and phosphate
In hydrogen, between two threads
G ionic

How many new single yarns are synthesized when doubling one molecule?
And four
B two
In one
R three

Which of the DNA doubling schemes is correct?
And the DNA molecule with doubling forms a completely new daughter molecule
B DNA subsidiary consists of one old and one new chain
In maternal DNA disintegrates into small fragments, which are then collected in new child molecules

Which fact confirms that DNA is a genetic material?
And the number of DNA in the cells of one organism is constantly
B DNA consists of nucleotides
In DNA localized in the core of the cell
DNA is a double spiral

In which of the named human cells is not DNA?
And mature leukocyte
B ripe red blood cell
In lymphocyte
G Neuron

If the nucleotide composition of DNA is ATT-GCH-TAT, then what should be the nucleotide composition of the IRNK?
TAA-CGC-Uta
B TAA-GCH-UTU
In UAA CGC-AU
G UAA CGC-Ata

Transcription is called:
And the education process of IRNA
B DNA doubling process
In the process of the formation of the protein chain on ribosomes
G TRNA connection process with amino acids

Synthesis IRNK begins:
And from the separation of the DNA molecule for two threads
B with doubling each thread
In with the interaction of RNA polymerase and gene
G from the splitting of the gene on nucleotides

The amino acid tryptophan is encoded by the UGG code. What is the DNA triplet carries information about this acid?
ACS
B TCC.
In UTS

Where is the IRNA synthesized?
And in ribosomes
B in cytoplasm
In in nucleoline
G in the nucleus

How will the IRNN chain section look like if the second nucleotide of the first triplet in DNA (HCT-AGT CCA) will be replaced by nucleotide t?
And CGA-UCA-GGT
B tsa-utsa-ggu
In GUU-AGU CTSA
Tstsu-Utsu-GSU

If the code was three, and four-letter, then how many combinations could be composed of this case from four nucleotides?
A 4 (4)
B 4 (16)
At 2 (4)
G 16 (3)

What information contains one DNA triplet?
And information about the sequence of amino acids in protein
B information about one sign of the body
To information about one amino acid included in the protein chain
R information about the start of the synthesis of IRNK

Which of the enzymes does the synthesis of IRNK?
And RNA synthetia
B RNA polymerase
In DNA polymerase

Genetic information is encoded in DNA. The genetic code was found out by M. Nirenberg and H.G. Quran, for which they were awarded Nobel Prize In 1968.

Genetic code - Nucleotide location system in nucleic acid molecules, which monitors the sequence of amino acids in the polypeptide molecule.

Basic postulates code:

1) The genetic code is triplet. Triplet and RNA received the name of the codon. The codon encrypts one amino acid.

2) Genetic code is degenerate. One amino acid is encrypted, more than one codon (from 2 to 6). Exceptions are methionine and tryptophan (AUG, GOG). In the codons for one amino acid, the first two nucleotides are most often the same, and the third varies.

3) Code do not overlap. The nucleotide sequence is read in one direction in a row, a triplet for a triplet.

4) The code is unambiguous. The codon encrypts a specific amino acid.

5) AUG is the starting codon.

6) Inside the gene there are no punctuation marks - Stop Codons: UAG, UAA, UAA.

7) The genetic code is universal, it is one for all organisms and viruses.

Disclosure The DNA structure, the material carrier of heredity contributed to the solution of many questions: reproduction of genes, the nature of mutations, protein biosynthesis, etc.

The genetic code transmission mechanism contributed to the development molecular biology, as well as genetic engineering, gene therapy.

DNA is in the kernel and is part of chromatin, as well as mitochondria, centrosome, plastists, and RNA - in nucleoli, matrix cytoplasm, ribosomes.

The carrier of hereditary information in the cell is DNA, and RNA - serves to transfer and implement genetic information from pro- and eukaryotes. With the help of and-RNA, the process of translation of the DNA nucleotide sequence in the polypeptide is taken.

In some organisms, in addition to DNA, the carrier of hereditary information may be RNA, for example, viruses of tobacco mosaic, poliomyelitis, AIDS.

Nucleic acid monomers are nucleotides. It has been established that in the chromosomes of eukaryota, a gigantic double DNA molecule is formed by 4 types of nucleotides: adenyl, guanilla, thymidyl, cytosyl. Each nucleotide consists of a nitrogen base (purine g + a or pyrimidine c + T), deoxyribose and phosphoric acid residue.

Analyzing DNA of various origins, Charguff formulated the patterns of quantitative ratio of nitrogen bases - Chargaff Rules.

a) the amount of adenine is equal to the amount of thymine (A \u003d T);

b) the amount of guanin is equal to the amount of cytosine (r \u003d c);

c) the amount of purines is equal to the amount of pyrimidines (g + a \u003d c + t);

d) the amount of bases with 6-amino groups is equal to the amount of bases with 6-keto groups (A + C \u003d r + T).

At the same time, the ratio of the bases of A + T \\ G + C is a strictly visual-specific coefficient (for a person - 0.66; mice - 0.81; bacteria - 0.41).

In 1953 by a biologist J.Uoton and physician F.Krikom. A spatial molecular DNA model was proposed.

The main postulates of the model are as follows:

1. Each DNA molecule consists of two long anti-parallel polynucleotide chains that form a double spiral, twisted around the central axis (human rights - in-form, left-handed-z-form, found by A. Rich in the late 70s).

2. Each nucleoside (pensose + nitrogen base) is located in the plane perpendicular to the axis of the spiral.

3. Two polynucleotide chains are fastened with hydrogen bonds formed between nitrogen bases.

4. Pairing nitrogenous bases is strictly specific, purin bases are connected only with pyrimidine: A-T, Mr.

5. The sequence of bases of one chain can vary significantly, but nitrogenous bases of another chain must be strictly complementary to them.

Polynucleotide chains are formed due to covalent bonds between adjacent nucleotides through the residue of phosphoric acid, which connects carbon in the fifth position of sugar with the third carbon of the adjacent nucleotide. Chains are elected: the beginning of the chain 3 "It is in the third position of the deoxyribose carbon. It is joined by a hydroxyl group.

Autosynthetic DNA function is replication - copyrofalization. Replication is based on the principles of semi-servers, anti-parallelity, complementarity and intermittentness. Hereditary information DNA is implemented as a result of replication by type matrix synthesis. It takes place in the stages: binding, initiation, elongation, termination. The process is timed to the s-period of the interphase. The DNA polymerase enzyme uses single-chain DNA as a matrix and in the presence of 4 nucleotides, the seed (RNA) builds the second DNA chain.

DNA synthesis is carried out according to the principle of complementarity. There is phosphodiester communication between the Nucleotides of the DNA chain due to the compounds 3 "it is the group of the most recent nucleotide with the 5" phosphate of the next nucleotide, which should join the chain.

The three main types of DNA replication are distinguished: conservative, semi-seruous, dispersed.

Conservative - The preservation of the integrity of the original two-chain molecule and the synthesis of a subsidiary. Half of the daughter molecules is completely built of new material, and half - from the old maternal.

Halfonsonvative - The synthesis of DNA begins with attachment to the point of the start of the replication of the enzyme Helichaza, which brings down the DNA sections. Each of the chains is joined by DNA binding protein (DSB), which prevents them with a compound. The replication unit is replicon - this is a plot between the two points of the beginning of the synthesis of the child chains. The interaction of enzymes with a point of the beginning of replication is called initiation. This point moves along the chain (3 "it → 5" f) and a replicative fork is formed.

The synthesis of the new chain is intermittent with the formation of fragments of a length of 700-800-2000 nucleotide residues. There is a point of the beginning and end of replication. The replicon moves along the DNA molecule and its new plots are broken. Each of the mother chains is a matrix for a subsidiary, which is synthesized according to the principle of complementarity. As a result of consecutive nucleotide compounds, the DNA chain is extended (stage of elongation) using the DNA ligase enzyme. When the desired length is reached, the synthesis molecule stops the termination. Eukarot employs thousands of replicative forks at once. Prokaryotes - initiation occurs at one point of the DNA ring, while two replicative forks move in 2 directions. At the place of their meeting, two DNA chain molecules are disconnected.

Dispersed - DNA disintegration on nucleotide fragments, new two-chain DNA consists of spontaneously gained new and parent fragments.

DNA eukaryota in structure is similar to DNA prokaryotes. The differences relate to: the amount of DNA on genes, the length of the DNA molecule, the order of alternation of nucleotide sequences, the form of laying (in eukaryota - linear, in prokaryotm - ring).

For eukaryotes, DNA redundancy is characterized: the amount of its DNA, which participates in coding is only 2%. Some of the excess DNA is represented by the same sets of nucleotides, repeating many times (repeats). There are multiple and moderately repetitive sequences. They form constitutional heterochromatin (structural). It is built into between unique sequences. Excessive genes have 10 4 copies.

Methazna chromosome (Spiralized chromatin) consists of two chromatids. The form is determined by the presence of primary drying - centromers. It shares the chromosome to 2 shoulders.

The location of the centrometers determines the main forms of chromosomes:

Metuclear,

Submetrical,

Acroccentric,

Bascentric.

The degree of spiralization chromosomes is not the same. Sections of chromosomes with weak spiralization call Eukhromatinov. This is a zone of high metabolic activity, where DNA consists of unique sequences. Zone with strong spiralization - heterochromatin Plot capable of transcription. Distinguish constitutive heterochromatin-genetic inert, does not contain genes, does not go into euchromatin, as well as optional, which can go to active eukhromatin. The end departments of distal sections chromosomes are called telomeres.

Chromosome are divided into autosomes (somatic cells) and heterochromosomes (genital cells).

At the proposal of Levitsky (1924), the diploid set of somatic chromosomes of the cell was named karyotype. It is characterized by a number, shape, chromosomes. To describe the karyotype chromosoma at the suggestion of this year. Navishashina they are posted as idiogram - Systematized karyotype. In 1960, a Denver International Classification of Chromosomes was proposed, where the chromosomes are classified by the magnitude and location of centromers. In the karyotype of the somatic cell of a person distinguish 22 pairs of autos and a pair of sex chromosomes. Set chromosomes in somatic cells called diploid, and in sex cells - haploid (It is equal to half a set of autosomes). In the human karyotype φiogram, chromosome are divided into 7 groups, depending on their size and form.

1 - 1-3 large meticenter.

2 - 4-5 large submetrical.

3 - 6-12 and X-chromosome medium meticenteric.

4 - 13-15 medium acrocentric.

5 - 16-18 relatively small meta-submet centers.

6 - 19-20 small metuclear.

7 - 21-22 and Y-chromosome are the smallest acrocentric.

According to Paris classification Chromosomes are divided into groups by their size and shape, as well as linear differentiation.

Chromosome possess the following properties (rules chromosomes):

1. Individuality - differences in non-homologous chromosomes.

2. Parity.

3. The consistency of the number is characteristic of each species.

4. Continuity - ability to reproduce.

Lesson on general biology.

Subject: "DNA is a carrier of hereditary information.

Genetic code".

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

Equipment: Table "The 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 early studied: ................................................. .... 12 min

2.2 Studying a new material: ..................................... ..................... 18 min

3. Fastening .............................................................................. .8 min

2.1. Repetition of previously studied

Questions to students:

1. What is proteins?
2. What is the monomers of all natural proteins? (20 amino acids).
3. Recall what functions are proteins? (Name the features of the structure of nucleic acids)
4. Recall where DNA molecules in plants and animals are contained?
5. What is complementaryness?
6. Name the types of RNA.

2.2. Studying a 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. Therefore, in the end, 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 organism proteins concluded in DNA molecules.

Gene - This is a portion of a DNA molecule encoding the primary structure of one polypeptide chain. DNA laid information about the primary protein structure.

Genetic code - A set of combinations of three nucleotides encoding 20 types of amino acids that are part of proteins.

Properties of the genetic code:

• Triplet code. Each AK (amino acid) corresponds to the DNA chain section, and, accordingly, the RNA of the three nearby nucleotides. Currently, the genetic code is fully deciphered and the map is compiled, that is, it is known which thrips correspond to a particular amino acid of 20, which are part of proteins.
• The code is unambiguous. Each codon encrypts only one AK.
• The code is redundant (specific). This means that each AK is encrypted by more than one codon (with the exception of methionine and tryptophan). DNA consists of 4 different species nucleotides, and the smallest structural unit of the gene is the nucleotide triplet. Therefore, the number of possible combinations is 43 \u003d 64. Different amino acids only 20. Thus, various nucleotide triplets with excess grabs for encoding 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, do not encode AK (consider in the textbook to the table of genetic code). These triplets are the synthesis of the synthesis of the polypeptide chain. The need for the presence of data of triplets is explained by the fact that in some cases the synthesis of several polypeptide chains is carried out on and-RNA, and these thrills are used to separate them from each other.
• Universal code. The genetic code is one for all living organisms living on Earth.

3. Fastening:

Exercises on the working notebook. (Workbook To the textbooks Zakharov V.B., Sukhova TS and etc.)

Homework.§ 2.10 p. 73-75, Tutorial V. B. Zakharova, S. G. Mamontova, N. I. Sonina, E. T. Zakharova Grade 10 "Biology. General biology", Abstract lesson.

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

Structural catalytic (b-enzymes) regulatory (b-hormones) contractile transport protective spare energy fkh n to c and and b e l to a

The structure of the NK RNA ________________________________ DNA a nitrogen base (a, g, c, y) residue FC carbohydrate - ribose nitrogenous base (A, G, T, T) carbohydrate - deoxyribosis residue FC

In chromosomes kernel

Complementation is the spatial complementarity of molecules or their parts, leading to the formation of hydrogen bonds. Complementary structures are suitable for each other as "key with lock" (A + T) + (g + C) \u003d 100%

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

Types of RNA in the cell there are several types of RNA. All of them are involved in the synthesis of protein. Transport RNA (T-RNA) is the smallest RNA in size. They associate AK and transport them to the place of protein synthesis. Information RNA (and-RNA) - they are 10 times more TRNA. Their function is to transfer information about the structure of protein from DNA to the site of protein synthesis. Ribosomal RNA (RNN) - have the greatest dimensions of the molecule, are part of the ribosomes.

The gene is a portion of a DNA molecule encoding the primary structure of one polypeptide chain genetic code - a set of combinations of three nucleotides encoding 20 types of amino acids that are part of proteins.

One amino acid is encoded with three nucleotides (one codon). ACT AGTS GAT Triplet, Code Code AK1 AK2 AK3 protein Properties of the genetic code: Triplet code. Each AK corresponds to the DNA chain section, and, accordingly, the RNA of the three nearby nucleotides.

The code is unambiguous. Each codon encrypts only one AK. The code is excessive. This means that each AK is encrypted by more than one codon (with the exception of methionine and tryptophan). The code is imperfect. Any nucleotide can be part of only one triplet. Between the genes there are "punctuation marks" (polarity). Of the 64 triplets -u-aa, ya-a-g, U -G, do not encode AK. Universal code. The genetic code is one for all living organisms living on Earth.

Homework Lesson Abstract Prepare Message: "Genetic Code".

Solving Tasks 1) Using the DNA genetic code table, determine which AK are encoded by triplets: CA, TTT, GAT. 2) Using the genetic code table, draw the DNA section in which information about the following sequence of amino acids in protein is encoded: - Alanine - Arginine - Valin - Glycine - lysine.

Plan lesson

• Chromosome - self-reproduced structural element The cell core containing DNA in which genetic (hereditary) information is enclosed.
• The number, size and shape of chromosome are strictly defined and specific for each species. Each chromosome consists of one or several pairs of chromon.
• Distinguish homologous

and non-homologous chromosomes

a brief description of

• For the first time chromosomes were described in the 80s. 19th century In the form of a compact chopped-shaped body, detected under the microscope in the core at a certain stage of cell division.
• Later it turned out that X. constantly available in each cell, but their appearance Significantly changing at different stages of cell life.
• It has been established that chromosomes are a thread-shaped structure of a huge length (chromatin thread), which can be spinning, forming a compact helix (spiralized), or unwind (despirate). Dense spiralization is carried out before the start of cell division and provides accurate redistribution of X. For subsidiaries.
• At the stage of mitotic division of chromosomes become visible in the light microscope. They can notice a plot called the centromer to which special threads are attached (spindle threads) involved in the "stretching" chromosome during cell division.
• The centrome is located in the center of X., making it into two equal shoulders, or can move to one of the ends. IN last case It is said that this X. Non-equation.
• As shown by the latest achievements of molecular genetics, chromosome is actually one long chromatin thread formed by a giant DNA molecule

Chromosome number of different species

• The number of chromosomes in all cells of each type of organisms is strictly constantly and is the exact characteristic of this type.

• Man (Homo Sapiens) 46
• Gorilla 48.
• Macaca (Macaca Mulatta) 42

• Animals
• Cat (Felis Domesticus) 38
• Dog (Canis Familiaris) 78
• Horse 64.
• Cow (Bovis Domesticus) 120
• Chicken (Gallus Domesticus) 78
• Pig 40.
• Fruit fly (D.Melanogaster) 8
• Mouse (Mus Musculus) 40
• Yeast (S.cerevisiae) 32
• Nematode 22/24.
• Rat 42.
• Fox 34.
• Dove 16.
• Carp 104.
• Midhoga 174.
• Frog (Rana Pipiens) 26
• Mixomycetes 14.
• Butterfly 380.
• Silkwall 56.
• Protea (Necturus Maculosis) 38
• Cancer (Cambarus Clarkii) 200
• Hydra 30.
• Askarida 2.
• Bee 16.
• Ant (Myrmecia Pilosula) 2
• Grape snail 24.
• Earthworm 36.
• River Cancer 1 16
• Malari plasma 2.
• Radiolaria 1600.

• Plants
• Clover 14.
• Toplar 38.
• Corn 20 (Zea Mays) 20
• Peas 14.
• Birch 84.
• Spruce 24.
• Onions (Allium CEPA) 16
• Arabidopsis (Arabidopsis Thaliana) 10
• Potatoes (S.Tuberosum) 48
• Lily 24.
• Horsetail field 216.

• Gooseberry 16.
• Cherry 32.
• Rye 14.
• Wheat 42.
• Fern ~ 1200.
• Linden heart-shaped 78.
• Iris Russian 80.
• Gladiolus ordinary 80.
• Clover Panneon 84.
• Heartbird Lake 90-180
• Alpine Krugtka 96-180
• Festik Japanese 104.
• Male shield 110.
• Barnets ordinary 144.
• Uzhomnik ordinary 164.
• Haplopappus 4.
• Arabidopsis Tal 6.

• The smallest number of chromosomes in the female subspecies of Murovyev Myrmecia Pilosula have a pair of chromosomes on the cage. The males have only 1 hosomes in each cell.
• The greatest number: the type of ferns Ophioglossum Reticulatum has about 630 pairs of chromosomes, or 1260 chromosomes on the cage
• The upper limit of the chromosome number does not depend on the number of DNA which includes: American amphibian Amphiuma DNA is ~ 30 times more than a person who is placed in 14 chromosomes.

Bacterial chromosomes

• Prokaryotes (archebacteria and bacteria, including mitochondria and plasts that constantly live in the cells of most eukaryotes) do not have chromosomes in their own sense of the word.
• In most of them, in the cell there is only one DNA macromolecule, closed in the ring (this structure was named nucleoid). A number of bacteria detected linear DNA macromolecules. In addition to the nucleoid or linear macromolecules, the DNA may be present in the cytoplasm of prokaryotic cells in the form of small DNA molecules closed into the ring, so-called plasmids containing usually insignificant, compared to bacterial chromosome, the number of genes. The composition of the plasmid may be inconsistent, bacteria can exchange plasmids during the parasoxual process.
• There are data on the presence of protein bacteria associated with the DNA of the nucleoid, but they have not been detected.

Chromosome eukarot

• Chromosome eukarot have complicated structure. The basis of the chromosome is the DNA linear macromolecule (in the human chromosome molecules, there is from 50 to 245 million pairs of nitrogen bases). In a stretched form, the length of the human chromosome can reach 5 cm. In addition to it, the chromosome includes five specialized proteins of histones - H1, H2A, H2B, H3 and H4 and a number of non-page proteins.
• In Interfase, chromatin is not condensed, but at this time its threads are a complex of DNA and proteins.
• In early interfax (phase G1), the basis of each of the future chromosomes is one DNA molecule. In the phase of synthesis (S), the DNA molecules come into the replication process and double. In the late interfax (phase G2), the basis of each chromosome consists of two identical DNA molecules formed as a result of replication and interconnected in the area of \u200b\u200bcentromeric sequence
• Before the start of division of the chromosome cell core, presented at this moment with a nucleosome chain, begins to spiral, or packaged, forming a thread thick chromatin thread with H1 protein, or chromatide, d \u003d 30 nm. As a result of further spiralization, chromatide diameter reaches the time of metafase 700 nm. Condensed chromosome has the appearance of the letter x (often with unequal shoulders), since two chromatids arising from replication are still interconnected in the center of the Centrometers (more on the fate of chromosomes with cellular division, see Mitosis and Meiosis)

Male chromosomal set of diploid (usual) cell

Note! Present both x and y-chromosome

Women's chromosomal set of diploid (usual) cell

Note! Only X-chromosomes are present.

Types of structure chromosomes

• There are four types of building chromosomes:

• bodycentric - chopped chromosomes with a centromer located at the proximal end);
• acrocentric - rod chromosomes with a very short, almost imperceptible second shoulder);
• sub present-centers - with the shoulders of unequal length, resembling the letter L);
• metic centers - V-shaped chromosomes with shoulders of equal length).

• The type of chromosomes is permanent for each homologous chromosome and can be permanent among all representatives of one type or kind

1 - equal depreciation (meticenter);

2 - inequalization (submetrical);

3 - chopstick (acrocentric);

4 - chromosomes with a secondary hawk.

Deoxyribonucleic acid

DNA - Biological polymer consisting of two spiral twisted chains

DNA structure

• DNA - polymer
• Monomers - nucleotides.
• Nucleotide - chemical compound Residues of three substances: nitrogen bases, carbohydrates, phosphoric acid residue

The structure of nucleotide

Azotista

basis :

Citzine

The residue of phosphoric acid

Carbohydrate :

Deoxyribese

Macromolecular structure of DNA

• In 1953, J.Uoton and F. Krik offered a DNA structure model. When building a structure, scientists were based on 4 data groups:

• DNA is a polymer consisting of nucleotides, connected 3 `- 5` - phosphodieter connections

2. The composition of DNA nucleotides is subordinate to Chargaff's rules:

(A + G) \u003d (T + C); number of residues a \u003d t, g \u003d c

3. DNA fiber radiographs indicate that the molecule has a spiral structure and contains more than one polynucleotide chain

4. Stability of the structure due to hydrogen bonds

Macromolecular DNA structure.

• the correct legal spiral consisting of 2 polynucleotide chains, which are spinning relative to each other around the common axis;
• chains have anti-parallel orientation
• pyrimidine and purine bases are stack with an interval of 0.34 nm;
• the length of the spiral turn is 3.40 nm.
• the presence of complimar pairs - the bases that form the pairs in which they are combined with hydrogen bonds

The gene is a part of a DNA molecule containing information about the structure of one protein-enzyme molecule.

He is the hereditary factor of any live body of nature.

In each cell, several thousand different protein molecules are synthesized.

Proteins are short-lived, the time of their existence is limited, after which they are destroyed.

Information about the sequence of amino acids in the protein molecule is encoded

in the form of a sequence of nucleotides in DNA.

In addition to proteins, the nucleotide DNA sequence encodes information on ribosomal RNA and transport RNA.

So, the sequence of nucleotides by somehow encodes the sequence of amino acids.

All protein varieties are formed from 20 different amino acids, and nucleotides in the DNA part - 4 species.

DNA code must be triplet. It was proved that it was three nucleotides to encode one amino acid, in this case it can be encoded

4 3 - 64 amino acids.

And since the amino acids are only 20, then some amino acids should be encoded by several triplets.

Properties of the genetic code:

• Triplet: Each amino acid is encoded by a nucleotide triplet - codon .
• Unambiguity: The code triplet, codon, corresponds to only one amino acid.
• Departure (redundancy): one amino acid can encode several (up to six) codons.

• Universality: The genetic code is the same, the same amino acids are encoded alone and the same nucleotide triplets in all the organisms of the Earth.
• Non-induction: The nucleotide sequence has a 3 nucleotide read frame, one and the same nucleotide may not be part of two triplets.

Properties of the genetic code:

• The presence of the initiator codon and code terminators: and C 64 code triplets 61 Codon - coding, encoded amino acids, and 3 - meaningless, do not encode amino acids, terminating the synthesis of the polypeptide during the operation of the ribosome (UAA, UAA, UEG). In addition, there is a codon - initiator (AUG) - methionine, from which the synthesis of any polypeptide begins.

2.1.1. DNA - carrier of hereditary information

"The DNA value is so great that no knowledge of it will be complete." F. Krik.

DNA - deoxyribonucleic acid - a biological macromolecule, a carrier of genetic information in all eukaryotic and prokaryotic cells and in many viruses.

In 1928, F. Griffith discovered the transformation phenomenon in pneumococci (transformation of bacteria properties). It showed that the cells of the unsecurable strains of bacteria (rough without capsules) acquire properties of virulent (smooth with capsules) of strains killed by heating. The nature of the transforming agent was established by Everi, Mac-Leod and Mac-picture in 1944, it turned out to be DNA. So the discovery and study of the transformation proved the role of DNA as a material carrier of hereditary information, (Fig. 2.1).

Fig.2.1. The transforming factor is DNA

The three-dimensional model of the spatial structure of double-stranded DNA was described in the April magazine Nature in 1953, J. Watson, Francis Creek and Maurice Wilkins. These studies have formed the basis of molecular biology that studies the basic properties and manifestations of life at the molecular level.

The structure of the DNA is a polymer, the structural unit of which is a nucleotide (Fig. 2.2).

The nucleotide consists of a nitrogen base of Pu-rinovoy: adenine (a) or guanine (g) or pyrimi-dynovoy: cytosine (C) or Timin (T), deoxyribose carbohydrates (five-carbon sugar ring) and phosphoric acid residue (NRU ~). Dual DNA Handicraft Spiral. 10 base pairs constitute a full turnover of 360 °, therefore, each pair of bases is rotated by 36 degrees around the spiral relative to the next pair. Phosphate groupings are outside the spirals outside, and the bases are inside and are located with an interval of 34 nm. Chains are held together with hydrogen bonds between the bases and are twisted one around the other and around the common axis.

Fig.2.2. DNA structure.

In the development of the DNA model, Chargaff (1949) was played by observations of Chargaff (1949) that Gaunin's quantitative relations are always equal to the content of cytosine, and the content of adenine corresponds to the content of thymine. This provision was called "Chargaff Rule":

those. The proportion of purine and pyrimidine bases is always equal.

Chargaffa for the characteristics of the nucleotide composition of DNA was proposed by the coefficient of specificity, taking into account the share of guanian-cytosine pairs:

Nucleotides are connected into a polynucleotide chain with bonds between 5 "positions of one pentosular end and 3" positions of the next pentosular ring through a phosphate group to form phosphodiester bridges, i.e. DNA sugar-phosphate cuns consists of 5-3 "connections. Genetic information is recorded in a sequence of nucleotides in the direction of 5" end to 3 "end - such a thread is called semantic DNA, there are genes of genes. The second filament of the direction 3-5 is considered antisense, But it is a necessary "benchmark" of storing genetic information. The antisense thread plays a large role in replication and reparation processes (restoration of the structure of damaged DNA). The bases in anti-parallel threads form complementary pairs of hydrogen bonds: a + t; G + c. Thus, the structure of one thread determines the sequence of nucleotides of another thread. Consequently, the base sequences in DNA threads are always anti-parallel and complementary.

The principle of complementarity is universal for replication and transcription processes.

Currently described several modifications of the DNA molecule.

Polymorphism DNA-

this ability of the molecule to take various configurations. Currently, 6 forms are described, some of which can only exist in vitro (in a test tube):

In-form- It has a standard structure, a practically appropriate DNA model, which was proposed by Watson, cry and Wilkins, in physiological conditions (low saline concentration, high degree of hydration) is the dominant structural type.

A-form -detected in more dehydrated media and with a higher content of potassium and sodium ions. Interesting from a biological point of view, because Its information is close to the structure of double-stranded DNA, or for DNA RNA duplexes.

C-form- It has fewer forms of reasons for a turn than a form. In these three forms there may be all DNA regardless of the nucleotide sequence. The following forms are characteristic only for DNA molecules with certain sequences in base pairs.

D.- and E-form- It is possible to extreme variants of the same shape, they have the smallest number of pairs of reasons for the turn (8 and 7.5). Detected only in DNA molecules not containing guanin.

Z.-the form- This is a zigzag form, with alternating levo and overallity. This form is detected with a number of factors: a high concentration of salts and the presence of specific cations; The high content of negative winds in the DNA molecule and other Z-DNA is found in areas enriched with M-C pairs. It is shown that the Z-form of DNA can participate in the regulation of gene expression of both closely arranged and substantially remote from Z-participle, as well as to play a significant role in the recombination processes.

Scottish scientist Arnott suggested: "It would be surprising if in the wilderness could not be used by this DNA ability to change its form."

Some of the forms can under certain conditions associated with changes in the concentration of salts and the degree of hydration, move into each other, for example, and<-> IN; as well as Z. <-> B. suggests that the mutual transitions of A- and B-forms regulate the work of genes. It is significant inThe human DNA has sections that are potentially capable of switching to Z-form, which are dispersed in the human genome.

It is assumed that in human cells there are conditions that stabilize the Z-form (Marri et al., 1993).

Table 2.1 Structural properties of some types of DNA

Knowledge of the structure and functions of the DNA are necessary to understand the essence of some genetic processes that are matrix. It was clear that the DNA itself cannot play the role of the matrix in the synthesis of proteins from amino acids, because Almost all it is in chromosomes located in the core, while most, if not all, cell proteins are synthesized in the cytoplasm. Thus, genetic information entered into DNA should be transmitted to some intermediate molecule, which would be transported to the cytoplasm and participated in the synthesis of polypeptide chains. The assumption that RNA may be such an intermediate molecule, it became serious to be considered as soon as the structure of the DNA double helix was opened. First, cells that synthesize a large amount of protein contained a lot of RNA. Secondly, it seemed even more important that DNA and RNA sacrahos-fate skeletons were extremely similar and it would be easy to imagine how the synthesis of single RNA chains on a single-stranded DNA with the formation of unstable hybrid molecules, one chain of which is presented DNA, and another RNA. The relationship between DNA, RNA and protein in 1953 was presented in the form of the following scheme:

dNA replication ..... Transcription -----> RNA ... Broadcast ......-\u003e Protein,

where single DNA chains serve as matrices in the synthesis of complementary DNA molecules (replication). In turn, RNA molecules serve as matrices for a sequential compound of amino acids to form polypeptide proteins in the transmission process, called so because "text" written in the "language" of nucleotides is translated (translated) to the "language" of amino acids. A group of nucleotides encoding one amino acid is called codon.