Examples of DNA and RNA. RNA and DNA

The times in which we live are marked by amazing changes, enormous progress, when people receive answers to more and more new questions. Life is rapidly moving forward, and what just recently seemed impossible is beginning to come true. It is quite possible that what today appears to be a plot from the fantasy genre will soon also acquire features of reality.

One of the most important discoveries in the second half of the twentieth century was the nucleic acids RNA and DNA, thanks to which man came closer to unraveling the secrets of nature.

Nucleic acids

Nucleic acids are organic compounds with high molecular weight properties. They contain hydrogen, carbon, nitrogen and phosphorus.

They were discovered in 1869 by F. Miescher, who examined pus. However, then their discovery was not given much importance. Only later, when these acids were discovered in all animal and plant cells, did their enormous role become understood.

There are two types of nucleic acids: RNA and DNA (ribonucleic and deoxyribonucleic acids). This article is devoted to ribonucleic acid, but for a general understanding, we will also consider what DNA is.

What's happened

DNA is made up of two strands that are connected according to the law of complementarity by hydrogen bonds of nitrogenous bases. The long chains are twisted into a spiral; one turn contains almost ten nucleotides. The diameter of the double helix is ​​two millimeters, the distance between nucleotides is about half a nanometer. The length of one molecule sometimes reaches several centimeters. The length of the DNA in the nucleus of a human cell is almost two meters.

The structure of DNA contains all DNA has replication, which means the process during which two completely identical daughter molecules are formed from one molecule.

As already noted, the chain is made up of nucleotides, which in turn consist of nitrogenous bases (adenine, guanine, thymine and cytosine) and a phosphorus acid residue. All nucleotides differ in their nitrogenous bases. Hydrogen bonding does not occur between all bases; adenine, for example, can only bond with thymine or guanine. Thus, there are as many adenyl nucleotides in the body as thymidyl nucleotides, and the number of guanyl nucleotides is equal to cytidyl nucleotides (Chargaff’s rule). It turns out that the sequence of one chain predetermines the sequence of another, and the chains seem to mirror each other. This pattern, where the nucleotides of two chains are arranged in an orderly manner and are also combined selectively, is called the principle of complementarity. In addition to hydrogen bonds, the double helix also interacts hydrophobically.

The two chains are multidirectional, that is, they are located in opposite directions. Therefore, opposite the three" end of one is the five" end of the other chain.

Outwardly, it resembles a spiral staircase, the railing of which is a sugar-phosphate frame, and the steps are complementary nitrogen bases.

What is ribonucleic acid?

RNA is a nucleic acid with monomers called ribonucleotides.

Its chemical properties are very similar to DNA, since both are polymers of nucleotides, which are a phospholated N-glycoside, which is built on a pentose residue (a five-carbon sugar), with a phosphate group at the fifth carbon atom and a nitrogen base at the first carbon atom.

It is a single polynucleotide chain (except for viruses), which is much shorter than DNA.

One RNA monomer is the remains of the following substances:

• nitrogen bases;
• five-carbon monosaccharide;
• phosphorus acids.

RNA has pyrimidine (uracil and cytosine) and purine (adenine, guanine) bases. Ribose is a monosaccharide nucleotide of RNA.

Differences between RNA and DNA

Nucleic acids differ from each other in the following properties:

• its quantity in a cell depends on the physiological state, age and organ affiliation;
• DNA contains the carbohydrate deoxyribose, and RNA contains ribose;
• the nitrogenous base in DNA is thymine, and in RNA it is uracil;
• classes perform different functions, but are synthesized on a DNA template;
• DNA consists of a double helix, while RNA consists of a single strand;
• it is not typical for it to act on DNA;
• RNA has more minor bases;
• the chains vary significantly in length.

History of the study

Cell RNA was first discovered by German biochemist R. Altmann while studying yeast cells. In the mid-twentieth century, the role of DNA in genetics was proven. Only then were the types of RNA, functions, and so on described. Up to 80-90% of the mass in the cell is r-RNA, which together with proteins forms a ribosome and participates in protein biosynthesis.

In the sixties of the last century, it was first suggested that there should be a certain species that carries the genetic information for protein synthesis. After this, it was scientifically established that there are such information ribonucleic acids that represent complementary copies of genes. They are also called messenger RNAs.

So-called transport acids are involved in decoding the information recorded in them.

Later, methods began to be developed to identify the nucleotide sequence and establish the structure of RNA in the acid space. Thus, it was discovered that some of them, called ribozymes, can cleave polyribonucleotide chains. As a result, it began to be assumed that at the time when life arose on the planet, RNA acted without DNA and proteins. Moreover, all transformations were carried out with her participation.

The structure of the ribonucleic acid molecule

Almost all RNA is a single chain of polynucleotides, which, in turn, consist of monoribonucleotides - purine and pyrimidine bases.

Nucleotides are designated by the initial letters of the bases:

• adenine (A), A;
• guanine (G), G;
• cytosine (C), C;
• uracil (U), U.

They are linked together by tri- and pentaphosphodiester bonds.

A very different number of nucleotides (from several tens to tens of thousands) are included in the structure of RNA. They can form a secondary structure consisting mainly of short double-stranded strands formed by complementary bases.

Structure of the ribnucleic acid molecule

As already mentioned, the molecule has a single-stranded structure. RNA receives its secondary structure and shape as a result of the interaction of nucleotides with each other. It is a polymer whose monomer is a nucleotide consisting of a sugar, a phosphorus acid residue and a nitrogen base. Externally, the molecule is similar to one of the DNA chains. The nucleotides adenine and guanine, which are part of RNA, are classified as purines. Cytosine and uracil are pyrimidine bases.

Synthesis process

For an RNA molecule to be synthesized, the template is a DNA molecule. However, the reverse process also happens, when new molecules of deoxyribonucleic acid are formed on the ribonucleic acid matrix. This occurs during the replication of some types of viruses.

Other ribonucleic acid molecules can also serve as the basis for biosynthesis. Many enzymes are involved in its transcription, which occurs in the cell nucleus, but the most important of them is RNA polymerase.

Kinds

Depending on the type of RNA, its functions also differ. There are several types:

• messenger RNA;
• ribosomal rRNA;
• transport tRNA;
• minor;
• ribozymes;
• viral.

Information ribonucleic acid

Such molecules are also called matrix molecules. They make up approximately two percent of the total number in the cell. In eukaryotic cells they are synthesized in the nuclei on DNA templates, then passing into the cytoplasm and binding to ribosomes. Next, they become templates for protein synthesis: transfer RNAs that carry amino acids are attached to them. This is how the process of converting information occurs, which is implemented in the unique structure of the protein. In some viral RNAs it is also a chromosome.

Jacob and Mano are the discoverers of this species. Without a rigid structure, its chain forms curved loops. When not working, mRNA gathers into folds and curls up into a ball, but unfolds when working.

mRNA carries information about the sequence of amino acids in the protein that is being synthesized. Each amino acid is encoded in a specific place using genetic codes, which are characterized by:

• triplet - it is possible to build sixty-four codons (genetic code) from four mononucleotides;
• non-crossing - information moves in one direction;
• continuity - the principle of operation is that one mRNA - one protein;
• universality - one or another type of amino acid is encoded in the same way in all living organisms;
• degeneracy - there are twenty known amino acids, and sixty-one codons, that is, they are encoded by several genetic codes.

Ribosomal ribonucleic acid

Such molecules make up the vast majority of cellular RNA, eighty to ninety percent of the total. They combine with proteins and form ribosomes - these are organelles that perform protein synthesis.

Ribosomes are composed of sixty-five percent rRNA and thirty-five percent protein. This polynucleotide chain easily bends along with the protein.

The ribosome consists of amino acid and peptide sections. They are located on contacting surfaces.

Ribosomes move freely in the right places. They are not very specific and can not only read information from mRNA, but also form a matrix with them.

Transport ribonucleic acid

tRNAs are the most studied. They make up ten percent of the cell's ribonucleic acid. These types of RNA bind to amino acids thanks to a special enzyme and are delivered to the ribosomes. In this case, amino acids are transported by transport molecules. However, it happens that different codons encode an amino acid. Then several transport RNAs will carry them.

It curls up into a ball when inactive, and when functioning it has the appearance of a clover leaf.

It distinguishes the following sections:

• an acceptor stem having the nucleotide sequence ACC;
• a site that serves to attach to a ribosome;
• an anticodon that codes for the amino acid that is attached to this tRNA.

Minor type of ribonucleic acid

Recently, RNA species have been added to a new class, the so-called small RNAs. They are most likely universal regulators that turn genes on or off in embryonic development, and also control processes within cells.

Ribozymes have also recently been identified; they actively participate when RNA acid is fermented, acting as a catalyst.

Viral types of acids

The virus is capable of containing either ribonucleic acid or deoxyribonucleic acid. Therefore, with the corresponding molecules, they are called RNA-containing. When such a virus enters a cell, reverse transcription occurs - new DNA appears on the basis of ribonucleic acid, which is integrated into the cells, ensuring the existence and reproduction of the virus. In another case, complementary RNA is formed on the incoming RNA. Viruses are proteins; life activity and reproduction occur without DNA, but only on the basis of the information contained in the RNA of the virus.

Replication

To improve our overall understanding, it is necessary to consider the process of replication that produces two identical nucleic acid molecules. This is how cell division begins.

It involves DNA polymerases, DNA-dependent, RNA polymerases and DNA ligases.

The replication process consists of the following steps:

• despiralization - there is a sequential unwinding of the maternal DNA, capturing the entire molecule;
• breaking of hydrogen bonds, in which the chains diverge and a replication fork appears;
• adjustment of dNTPs to the released bases of the mother chains;
• the cleavage of pyrophosphates from dNTP molecules and the formation of phosphodiester bonds due to the released energy;
• respiralization.

After the formation of a daughter molecule, the nucleus, cytoplasm and the rest are divided. Thus, two daughter cells are formed that have fully received all the genetic information.

In addition, the primary structure of proteins that are synthesized in the cell is encoded. DNA takes an indirect part in this process, and not a direct one, which consists in the fact that it is on DNA that the synthesis of RNA and proteins involved in the formation takes place. This process is called transcription.

Transcription

The synthesis of all molecules occurs during transcription, that is, the rewriting of genetic information from a specific DNA operon. The process is similar to replication in some ways and quite different in others.

The similarities are the following parts:

• the beginning comes from the despiralization of DNA;
• hydrogen bonds between the bases of the chains are broken;
• NTFs are complementarily adjusted to them;
• hydrogen bonds are formed.

Differences from replication:

• during transcription, only the DNA section corresponding to the transcripton is unraveled, while during replication, the entire molecule is untwisted;
• during transcription, the adapting NTPs contain ribose and uracil instead of thymine;
• information is written off only from a certain area;
• Once the molecule is formed, the hydrogen bonds and the synthesized chain are broken, and the chain slips off the DNA.

For normal functioning, the primary structure of RNA must consist only of DNA sections copied from exons.

Newly formed RNAs begin the process of maturation. Silent sections are cut out, and informative sections are stitched together, forming a polynucleotide chain. Further, each species has transformations unique to it.

In mRNA, attachment occurs at the initial end. The polyadenylate is attached to the final section.

In tRNA, bases are modified to form minor species.

In rRNA, individual bases are also methylated.

Protects proteins from destruction and improves transport into the cytoplasm. RNA in a mature state combines with them.

The meaning of deoxyribonucleic acids and ribonucleic acids

Nucleic acids are of great importance in the life of organisms. They store information about proteins synthesized in each cell, transferred to the cytoplasm, and inherited by daughter cells. They are present in all living organisms; the stability of these acids plays a critical role for the normal functioning of both cells and the entire organism. Any changes in their structure will lead to cellular changes.

4.2.1. Primary structure of nucleic acids called sequence of arrangement of mononucleotides in a DNA or RNA chain . The primary structure of nucleic acids is stabilized by 3",5" phosphodiester bonds. These bonds are formed by the interaction of the hydroxyl group in the 3" position of the pentose residue of each nucleotide with the phosphate group of the neighboring nucleotide (Figure 3.2),

Thus, at one end of the polynucleotide chain there is a free 5"-phosphate group (5"-end), and at the other there is a free hydroxyl group in the 3" position (3"-end). Nucleotide sequences are usually written in the direction from the 5" end to the 3" end.

Figure 4.2. The structure of a dinucleotide, which includes adenosine 5"-monophosphate and cytidine 5"-monophosphate.

4.2.2. DNA (deoxyribonucleic acid) found in the cell nucleus and has a molecular weight of about 1011 Da. Its nucleotides contain nitrogenous bases adenine, guanine, cytosine, thymine , carbohydrate deoxyribose and phosphoric acid residues. The content of nitrogenous bases in a DNA molecule is determined by Chargaff’s rules:

1) the number of purine bases is equal to the number of pyrimidine bases (A + G = C + T);

2) the amount of adenine and cytosine is equal to the amount of thymine and guanine, respectively (A = T; C = G);

3) DNA isolated from cells of different biological species differ from each other in the specificity coefficient:

(G + C) / (A + T)

These patterns in the structure of DNA are explained by the following features of its secondary structure:

1) a DNA molecule is built from two polynucleotide chains connected to each other by hydrogen bonds and oriented antiparallel (that is, the 3" end of one chain is located opposite the 5" end of the other chain and vice versa);

2) hydrogen bonds are formed between complementary pairs of nitrogenous bases. Thymine is complementary to adenine; this pair is stabilized by two hydrogen bonds. Cytosine is complementary to guanine; this pair is stabilized by three hydrogen bonds (see figure b). The more G-C pairs in a DNA molecule, the greater its resistance to high temperatures and ionizing radiation;

Figure 3.3. Hydrogen bonds between complementary nitrogenous bases.

3) both DNA strands are twisted into a helix that has a common axis. The nitrogenous bases face the inside of the helix; In addition to hydrogen interactions, hydrophobic interactions also arise between them. The ribose phosphate moieties are located along the periphery, forming the core of the helix (see Figure 3.4).

Figure 3.4. DNA structure diagram.

4.2.3. RNA (ribonucleic acid) is found predominantly in the cytoplasm of the cell and has a molecular weight in the range of 104 - 106 Da. Its nucleotides contain nitrogenous bases adenine, guanine, cytosine, uracil , carbohydrate ribose and phosphoric acid residues. Unlike DNA, RNA molecules are built from a single polynucleotide chain, which can contain sections that are complementary to each other (Figure 3.5). These regions can interact with each other, forming double helices alternating with non-helical regions.

Figure 3.5. Scheme of the structure of transfer RNA.

Based on their structure and function, there are three main types of RNA:

1) messenger RNA (mRNA) transmit information about the structure of the protein from the cell nucleus to ribosomes;

2) transfer RNAs (tRNAs) transport amino acids to the site of protein synthesis;

3) ribosomal RNA (rRNA) are part of ribosomes and participate in protein synthesis.

On the right is the largest helix of human DNA, built from people on the beach in Varna (Bulgaria), included in the Guinness Book of Records on April 23, 2016

Deoxyribonucleic acid. General information

DNA (deoxyribonucleic acid) is a kind of blueprint for life, a complex code that contains data on hereditary information. This complex macromolecule is capable of storing and transmitting hereditary genetic information from generation to generation. DNA determines such properties of any living organism as heredity and variability. The information encoded in it sets the entire development program of any living organism. Genetically determined factors predetermine the entire course of life of both a person and any other organism. Artificial or natural influences of the external environment can only slightly affect the overall expression of individual genetic traits or affect the development of programmed processes.

Deoxyribonucleic acid(DNA) is a macromolecule (one of the three main ones, the other two are RNA and proteins) that ensures storage, transmission from generation to generation and implementation of the genetic program for the development and functioning of living organisms. DNA contains information about the structure of various types of RNA and proteins.

In eukaryotic cells (animals, plants and fungi), DNA is found in the cell nucleus as part of chromosomes, as well as in some cellular organelles (mitochondria and plastids). In the cells of prokaryotic organisms (bacteria and archaea), a circular or linear DNA molecule, the so-called nucleoid, is attached from the inside to the cell membrane. In them and in lower eukaryotes (for example, yeast), small autonomous, predominantly circular DNA molecules called plasmids are also found.

From a chemical point of view, DNA is a long polymer molecule consisting of repeating blocks called nucleotides. Each nucleotide consists of a nitrogenous base, a sugar (deoxyribose) and a phosphate group. The bonds between nucleotides in the chain are formed due to deoxyribose ( WITH) and phosphate ( F) groups (phosphodiester bonds).

Rice. 2. A nucleotide consists of a nitrogenous base, a sugar (deoxyribose) and a phosphate group

In the vast majority of cases (except for some viruses containing single-stranded DNA), the DNA macromolecule consists of two chains oriented with nitrogenous bases towards each other. This double-stranded molecule is twisted along a helix.

There are four types of nitrogenous bases found in DNA (adenine, guanine, thymine and cytosine). The nitrogenous bases of one of the chains are connected to the nitrogenous bases of the other chain by hydrogen bonds according to the principle of complementarity: adenine combines only with thymine ( A-T), guanine - only with cytosine ( G-C). It is these pairs that make up the “rungs” of the DNA spiral “staircase” (see: Fig. 2, 3 and 4).

Rice. 2. Nitrogenous bases

The sequence of nucleotides allows you to “encode” information about various types of RNA, the most important of which are messenger or template (mRNA), ribosomal (rRNA) and transport (tRNA). All these types of RNA are synthesized on a DNA template by copying a DNA sequence into an RNA sequence synthesized during transcription, and take part in protein biosynthesis (the translation process). In addition to coding sequences, cell DNA contains sequences that perform regulatory and structural functions.

Rice. 3. DNA replication

The arrangement of basic combinations of DNA chemical compounds and the quantitative relationships between these combinations ensure the coding of hereditary information.

Education new DNA (replication)

1. Replication process: unwinding of the DNA double helix - synthesis of complementary strands by DNA polymerase - formation of two DNA molecules from one.
2. The double helix "unzips" into two branches when enzymes break the bond between the base pairs of chemical compounds.
3. Each branch is an element of new DNA. New base pairs are connected in the same sequence as in the parent branch.

Upon completion of duplication, two independent helices are formed, created from chemical compounds of the parent DNA and having the same genetic code. In this way, DNA is able to pass information from cell to cell.

More detailed information:

STRUCTURE OF NUCLEIC ACIDS

Rice. 4 . Nitrogen bases: adenine, guanine, cytosine, thymine

Deoxyribonucleic acid(DNA) refers to nucleic acids. Nucleic acids are a class of irregular biopolymers whose monomers are nucleotides.

NUCLEOTIDES consist of nitrogenous base, connected to a five-carbon carbohydrate (pentose) - deoxyribose(in case of DNA) or ribose(in the case of RNA), which combines with a phosphoric acid residue (H 2 PO 3 -).

Nitrogenous bases There are two types: pyrimidine bases - uracil (only in RNA), cytosine and thymine, purine bases - adenine and guanine.

Rice. 5. Structure of nucleotides (left), location of the nucleotide in DNA (bottom) and types of nitrogenous bases (right): pyrimidine and purine

The carbon atoms in the pentose molecule are numbered from 1 to 5. The phosphate combines with the third and fifth carbon atoms. This is how nucleinotides are combined into a nucleic acid chain. Thus, we can distinguish the 3' and 5' ends of the DNA strand:

Rice. 6. Isolation of the 3' and 5' ends of the DNA chain

Two strands of DNA form double helix. These chains in the spiral are oriented in opposite directions. In different strands of DNA, nitrogenous bases are connected to each other by hydrogen bonds. Adenine always pairs with thymine, and cytosine always pairs with guanine. It is called complementarity rule.

Complementarity rule:

A-T G-C

For example, if we are given a DNA strand with the sequence

3’- ATGTCCTAGCTGCTCG - 5’,

then the second chain will be complementary to it and directed in the opposite direction - from the 5’ end to the 3’ end:

5'- TACAGGATCGACGAGC- 3'.

Rice. 7. Direction of the chains of the DNA molecule and the connection of nitrogenous bases using hydrogen bonds

DNA REPLICATION

DNA replication is the process of doubling a DNA molecule through template synthesis. In most cases of natural DNA replicationprimerfor DNA synthesis is short fragment (recreated). Such a ribonucleotide primer is created by the enzyme primase (DNA primase in prokaryotes, DNA polymerase in eukaryotes), and is subsequently replaced by deoxyribonucleotide polymerase, which normally performs repair functions (correcting chemical damage and breaks in the DNA molecule).

Replication occurs according to a semi-conservative mechanism. This means that the double helix of DNA unwinds and a new chain is built on each of its chains according to the principle of complementarity. The daughter DNA molecule thus contains one strand from the parent molecule and one newly synthesized one. Replication occurs in the direction from the 3' to the 5' end of the mother strand.

Rice. 8. Replication (doubling) of a DNA molecule

DNA synthesis- this is not as complicated a process as it might seem at first glance. If you think about it, first you need to figure out what synthesis is. This is the process of combining something into one whole. The formation of a new DNA molecule occurs in several stages:

1) DNA topoisomerase, located in front of the replication fork, cuts the DNA in order to facilitate its unwinding and unwinding.
2) DNA helicase, following topoisomerase, influences the process of “unbraiding” of the DNA helix.
3) DNA-binding proteins bind DNA strands and also stabilize them, preventing them from sticking to each other.
4) DNA polymerase δ(delta) , coordinated with the speed of movement of the replication fork, carries out synthesisleadingchains subsidiary DNA in the 5"→3" direction on the matrix maternal DNA strands in the direction from its 3" end to the 5" end (speed up to 100 nucleotide pairs per second). These events at this maternal DNA strands are limited.

Rice. 9. Schematic representation of the DNA replication process: (1) Lagging strand (lagging strand), (2) Leading strand (leading strand), (3) DNA polymerase α (Polα), (4) DNA ligase, (5) RNA -primer, (6) Primase, (7) Okazaki fragment, (8) DNA polymerase δ (Polδ), (9) Helicase, (10) Single-stranded DNA-binding proteins, (11) Topoisomerase.

The synthesis of the lagging strand of daughter DNA is described below (see. Scheme replication fork and functions of replication enzymes)

For more information about DNA replication, see

5) Immediately after the other strand of the mother molecule is unraveled and stabilized, it is attached to itDNA polymerase α(alpha)and in the 5"→3" direction it synthesizes a primer (RNA primer) - an RNA sequence on a DNA template with a length of 10 to 200 nucleotides. After this the enzymeremoved from the DNA strand.

Instead of DNA polymerasesα is attached to the 3" end of the primer DNA polymeraseε .

6) DNA polymeraseε (epsilon) seems to continue to extend the primer, but inserts it as a substratedeoxyribonucleotides(in the amount of 150-200 nucleotides). As a result, a single thread is formed from two parts -RNA(i.e. primer) and DNA. DNA polymerase εruns until it encounters the previous primerfragment of Okazaki(synthesized a little earlier). After this, this enzyme is removed from the chain.

7) DNA polymerase β(beta) stands insteadDNA polymerase ε,moves in the same direction (5"→3") and removes the primer ribonucleotides while simultaneously inserting deoxyribonucleotides in their place. The enzyme works until the primer is completely removed, i.e. until a deoxyribonucleotide (an even earlier synthesizedDNA polymerase ε). The enzyme is not able to connect the result of its work with the DNA in front, so it goes off the chain.

As a result, a fragment of daughter DNA “lies” on the matrix of the mother strand. It is calledfragment of Okazaki.

8) DNA ligase crosslinks two adjacent fragments of Okazaki , i.e. 5" end of the segment synthesizedDNA polymerase ε,and 3"-end chain built-inDNA polymeraseβ .

STRUCTURE OF RNA

Ribonucleic acid(RNA) is one of the three main macromolecules (the other two are DNA and proteins) that are found in the cells of all living organisms.

Just like DNA, RNA consists of a long chain in which each link is called nucleotide. Each nucleotide consists of a nitrogenous base, a ribose sugar, and a phosphate group. However, unlike DNA, RNA usually has one strand rather than two. The pentose in RNA is ribose, not deoxyribose (ribose has an additional hydroxyl group on the second carbohydrate atom). Finally, DNA differs from RNA in the composition of nitrogenous bases: instead of thymine ( T) RNA contains uracil ( U) , which is also complementary to adenine.

The sequence of nucleotides allows RNA to encode genetic information. All cellular organisms use RNA (mRNA) to program protein synthesis.

Cellular RNA is produced through a process called transcription , that is, the synthesis of RNA on a DNA matrix, carried out by special enzymes - RNA polymerases.

Messenger RNAs (mRNAs) then take part in a process called broadcast, those. protein synthesis on an mRNA matrix with the participation of ribosomes. Other RNAs undergo chemical modifications after transcription, and after the formation of secondary and tertiary structures, they perform functions depending on the type of RNA.

Rice. 10. The difference between DNA and RNA in the nitrogenous base: instead of thymine (T), RNA contains uracil (U), which is also complementary to adenine.

TRANSCRIPTION

This is the process of RNA synthesis on a DNA template. DNA unwinds at one of the sites. One of the strands contains information that needs to be copied onto an RNA molecule - this strand is called the coding strand. The second strand of DNA, complementary to the coding one, is called the template. During transcription, a complementary RNA chain is synthesized on the template strand in the 3’ - 5’ direction (along the DNA strand). This creates an RNA copy of the coding strand.

Rice. 11. Schematic representation of the transcription

For example, if we are given the sequence of the coding chain

3’- ATGTCCTAGCTGCTCG - 5’,

then, according to the complementarity rule, the matrix chain will carry the sequence

5’- TACAGGATCGACGAGC- 3’,

and the RNA synthesized from it is the sequence

BROADCAST

Let's consider the mechanism protein synthesis on the RNA matrix, as well as the genetic code and its properties. Also, for clarity, at the link below, we recommend watching a short video about the processes of transcription and translation occurring in a living cell:

Rice. 12. Protein synthesis process: DNA codes for RNA, RNA codes for protein

GENETIC CODE

Genetic code- a method of encoding the amino acid sequence of proteins using a sequence of nucleotides. Each amino acid is encoded by a sequence of three nucleotides - a codon or triplet.

Genetic code common to most pro- and eukaryotes. The table shows all 64 codons and the corresponding amino acids. The base order is from the 5" to the 3" end of the mRNA.

Table 1. Standard genetic code

1st the basis tion	2nd base								3rd the basis tion
	U		C		A		G
U	U U U	(Phe/F)	U C U	(Ser/S)	U A U	(Tyr/Y)	U G U	(Cys/C)	U
	U U C		U C C		U A C		U G C		C
	U U A	(Leu/L)	U C A		U A A	Stop codon**	U G A	Stop codon**	A
	U U G		U C G		U A G	Stop codon**	U G G	(Trp/W)	G
C	C U U		C C U	(Pro/P)	C A U	(His/H)	C G U	(Arg/R)	U
	C U C		C C C		C A C		C G C		C
	C U A		C C A		C A A	(Gln/Q)	C GA		A
	C U G		C C G		C A G		C G G		G
A	A U U	(Ile/I)	A C U	(Thr/T)	A A U	(Asn/N)	A G U	(Ser/S)	U
	A U C		A C C		A A C		A G C		C
	A U A		A C A		A A A	(Lys/K)	A G A		A
	A U G	(Met/M)	A C G		A A G		A G G		G
G	G U U	(Val/V)	G C U	(Ala/A)	G A U	(Asp/D)	G G U	(Gly/G)	U
	G U C		G C C		G A C		G G C		C
	G U A		G C A		G A A	(Glu/E)	G G A		A
	G U G		G C G		G A G		G G G		G

Among the triplets, there are 4 special sequences that serve as “punctuation marks”:

• *Triplet AUG, also encoding methionine, is called start codon. The synthesis of a protein molecule begins with this codon. Thus, during protein synthesis, the first amino acid in the sequence will always be methionine.

• **Triplets UAA, UAG And U.G.A. are called stop codons and do not code for a single amino acid. At these sequences, protein synthesis stops.

Properties of the genetic code

1. Triplety. Each amino acid is encoded by a sequence of three nucleotides - a triplet or codon.

2. Continuity. There are no additional nucleotides between the triplets; the information is read continuously.

3. Non-overlapping. One nucleotide cannot be included in two triplets at the same time.

4. Unambiguity. One codon can code for only one amino acid.

5. Degeneracy. One amino acid can be encoded by several different codons.

6. Versatility. The genetic code is the same for all living organisms.

Example. We are given the sequence of the coding chain:

3’- CCGATTGCACGTCGATCGTATA- 5’.

The matrix chain will have the sequence:

5’- GGCTAACGTGCAGCTAGCATAT- 3’.

Now we “synthesize” information RNA from this chain:

3’- CCGAUUGCACGUCGAUCGUAUA- 5’.

Protein synthesis proceeds in the direction 5’ → 3’, therefore, we need to reverse the sequence to “read” the genetic code:

5’- AUAUGCUAGCUGCACGUUAGCC- 3’.

Now let's find the start codon AUG:

5’- AU AUG CUAGCUGCACGUUAGCC- 3’.

Let's divide the sequence into triplets:

sounds like this: information is transferred from DNA to RNA (transcription), from RNA to protein (translation). DNA can also be duplicated by replication, and the process of reverse transcription is also possible, when DNA is synthesized from an RNA template, but this process is mainly characteristic of viruses.

Rice. 13. Central Dogma of Molecular Biology

GENOME: GENES and CHROMOSOMES

(general concepts)

Genome - the totality of all the genes of an organism; its complete chromosome set.

The term “genome” was proposed by G. Winkler in 1920 to describe the set of genes contained in the haploid set of chromosomes of organisms of one biological species. The original meaning of this term indicated that the concept of a genome, in contrast to a genotype, is a genetic characteristic of the species as a whole, and not of an individual. With the development of molecular genetics, the meaning of this term has changed. It is known that DNA, which is the carrier of genetic information in most organisms and, therefore, forms the basis of the genome, includes not only genes in the modern sense of the word. Most of the DNA of eukaryotic cells is represented by non-coding (“redundant”) nucleotide sequences that do not contain information about proteins and nucleic acids. Thus, the main part of the genome of any organism is the entire DNA of its haploid set of chromosomes.

Genes are sections of DNA molecules that encode polypeptides and RNA molecules

Over the last century, our understanding of genes has changed significantly. Previously, a genome was a region of a chromosome that encodes or defines one characteristic or phenotypic(visible) property, such as eye color.

In 1940, George Beadle and Edward Tatham proposed a molecular definition of the gene. Scientists processed fungal spores Neurospora crassa X-rays and other agents that cause changes in the DNA sequence ( mutations), and discovered mutant strains of the fungus that had lost some specific enzymes, which in some cases led to disruption of the entire metabolic pathway. Beadle and Tatem concluded that a gene is a piece of genetic material that specifies or codes for a single enzyme. This is how the hypothesis appeared "one gene - one enzyme". This concept was later expanded to define "one gene - one polypeptide", since many genes encode proteins that are not enzymes, and the polypeptide may be a subunit of a complex protein complex.

In Fig. Figure 14 shows a diagram of how triplets of nucleotides in DNA determine a polypeptide - the amino acid sequence of a protein through the mediation of mRNA. One of the DNA chains plays the role of a template for the synthesis of mRNA, the nucleotide triplets (codons) of which are complementary to the DNA triplets. In some bacteria and many eukaryotes, coding sequences are interrupted by non-coding regions (called introns).

Modern biochemical determination of the gene even more specific. Genes are all sections of DNA that encode the primary sequence of end products, which include polypeptides or RNA that have a structural or catalytic function.

Along with genes, DNA also contains other sequences that perform exclusively a regulatory function. Regulatory sequences may mark the beginning or end of genes, influence transcription, or indicate the site of initiation of replication or recombination. Some genes can be expressed in different ways, with the same DNA region serving as a template for the formation of different products.

We can roughly calculate minimum gene size, encoding the middle protein. Each amino acid in a polypeptide chain is encoded by a sequence of three nucleotides; the sequences of these triplets (codons) correspond to the chain of amino acids in the polypeptide that is encoded by this gene. A polypeptide chain of 350 amino acid residues (medium length chain) corresponds to a sequence of 1050 bp. ( base pairs). However, many eukaryotic genes and some prokaryotic genes are interrupted by DNA segments that do not carry protein information, and therefore turn out to be much longer than a simple calculation shows.

How many genes are on one chromosome?

Rice. 15. View of chromosomes in prokaryotic (left) and eukaryotic cells. Histones are a large class of nuclear proteins that perform two main functions: they participate in the packaging of DNA strands in the nucleus and in the epigenetic regulation of nuclear processes such as transcription, replication and repair.

As is known, bacterial cells have a chromosome in the form of a DNA strand arranged in a compact structure - a nucleoid. Prokaryotic chromosome Escherichia coli, whose genome has been completely deciphered, is a circular DNA molecule (in fact, it is not a perfect circle, but rather a loop without a beginning or end), consisting of 4,639,675 bp. This sequence contains approximately 4,300 protein genes and another 157 genes for stable RNA molecules. IN human genome approximately 3.1 billion base pairs corresponding to nearly 29,000 genes located on 24 different chromosomes.

Prokaryotes (Bacteria).

Bacterium E. coli has one double-stranded circular DNA molecule. It consists of 4,639,675 bp. and reaches a length of approximately 1.7 mm, which exceeds the length of the cell itself E. coli approximately 850 times. In addition to the large circular chromosome as part of the nucleoid, many bacteria contain one or several small circular DNA molecules that are freely located in the cytosol. These extrachromosomal elements are called plasmids(Fig. 16).

Most plasmids consist of only a few thousand base pairs, some contain more than 10,000 bp. They carry genetic information and replicate to form daughter plasmids, which enter the daughter cells during the division of the parent cell. Plasmids are found not only in bacteria, but also in yeast and other fungi. In many cases, plasmids provide no benefit to the host cells and their sole purpose is to reproduce independently. However, some plasmids carry genes beneficial to the host. For example, genes contained in plasmids can make bacterial cells resistant to antibacterial agents. Plasmids carrying the β-lactamase gene provide resistance to β-lactam antibiotics such as penicillin and amoxicillin. Plasmids can pass from cells that are resistant to antibiotics to other cells of the same or a different species of bacteria, causing those cells to also become resistant. Intensive use of antibiotics is a powerful selective factor that promotes the spread of plasmids encoding antibiotic resistance (as well as transposons that encode similar genes) among pathogenic bacteria, leading to the emergence of bacterial strains with resistance to multiple antibiotics. Doctors are beginning to understand the dangers of widespread use of antibiotics and prescribe them only in cases of urgent need. For similar reasons, the widespread use of antibiotics to treat farm animals is limited.

See also: Ravin N.V., Shestakov S.V. Genome of prokaryotes // Vavilov Journal of Genetics and Breeding, 2013. T. 17. No. 4/2. pp. 972-984.

Eukaryotes.

Table 2. DNA, genes and chromosomes of some organisms

	Shared DNA p.n.	Number of chromosomes*	Approximate number of genes
Escherichia coli(bacterium)	4 639 675		4 435
Saccharomyces cerevisiae(yeast)	12 080 000	16**	5 860
Caenorhabditis elegans(nematode)	90 269 800	12***	23 000
Arabidopsis thaliana(plant)	119 186 200		33 000
Drosophila melanogaster(fruit fly)	120 367 260		20 000
Oryza sativa(rice)	480 000 000		57 000
Mus musculus(mouse)	2 634 266 500		27 000
Homo sapiens(Human)	3 070 128 600		29 000

Note. Information is constantly updated; For more up-to-date information, refer to individual genomics project websites

* For all eukaryotes, except yeast, the diploid set of chromosomes is given. Diploid kit chromosomes (from the Greek diploos - double and eidos - species) - a double set of chromosomes (2n), each of which has a homologous one.
**Haploid set. Wild yeast strains typically have eight (octaploid) or more sets of these chromosomes.
***For females with two X chromosomes. Males have an X chromosome, but no Y, i.e. only 11 chromosomes.

Yeast, one of the smallest eukaryotes, has 2.6 times more DNA than E. coli(Table 2). Fruit fly cells Drosophila, a classic subject of genetic research, contain 35 times more DNA, and human cells contain approximately 700 times more DNA than E. coli. Many plants and amphibians contain even more DNA. The genetic material of eukaryotic cells is organized in the form of chromosomes. Diploid set of chromosomes (2 n) depends on the type of organism (Table 2).

For example, a human somatic cell has 46 chromosomes ( rice. 17). Each chromosome of a eukaryotic cell, as shown in Fig. 17, A, contains one very large double-stranded DNA molecule. Twenty-four human chromosomes (22 paired chromosomes and two sex chromosomes X and Y) vary in length by more than 25 times. Each eukaryotic chromosome contains a specific set of genes.

Rice. 17. Chromosomes of eukaryotes.A- a pair of linked and condensed sister chromatids from the human chromosome. In this form, eukaryotic chromosomes remain after replication and in metaphase during mitosis. b- a complete set of chromosomes from a leukocyte of one of the authors of the book. Each normal human somatic cell contains 46 chromosomes.

If you connect the DNA molecules of the human genome (22 chromosomes and chromosomes X and Y or X and X), you get a sequence about one meter long. Note: In all mammals and other heterogametic male organisms, females have two X chromosomes (XX) and males have one X chromosome and one Y chromosome (XY).

Most human cells, so the total DNA length of such cells is about 2 m. An adult human has approximately 10 14 cells, so the total length of all DNA molecules is 2・10 11 km. For comparison, the circumference of the Earth is 4・10 4 km, and the distance from the Earth to the Sun is 1.5・10 8 km. This is how amazingly compact DNA is packed in our cells!

In eukaryotic cells there are other organelles containing DNA - mitochondria and chloroplasts. Many hypotheses have been put forward regarding the origin of mitochondrial and chloroplast DNA. The generally accepted point of view today is that they represent the rudiments of the chromosomes of ancient bacteria, which penetrated the cytoplasm of the host cells and became the precursors of these organelles. Mitochondrial DNA encodes mitochondrial tRNAs and rRNAs, as well as several mitochondrial proteins. More than 95% of mitochondrial proteins are encoded by nuclear DNA.

STRUCTURE OF GENES

Let's consider the structure of the gene in prokaryotes and eukaryotes, their similarities and differences. Despite the fact that a gene is a section of DNA that encodes only one protein or RNA, in addition to the immediate coding part, it also includes regulatory and other structural elements that have different structures in prokaryotes and eukaryotes.

Coding sequence- the main structural and functional unit of the gene, it is in it that the triplets of nucleotides encoding are locatedamino acid sequence. It begins with a start codon and ends with a stop codon.

Before and after the coding sequence there are untranslated 5' and 3' sequences. They perform regulatory and auxiliary functions, for example, ensuring the landing of the ribosome on mRNA.

Untranslated and coding sequences make up the transcription unit - the transcribed section of DNA, that is, the section of DNA from which mRNA synthesis occurs.

Terminator- a non-transcribed section of DNA at the end of a gene where RNA synthesis stops.

At the beginning of the gene is regulatory region, which includes promoter And operator.

Promoter- the sequence to which the polymerase binds during transcription initiation. Operator- this is an area that special proteins can bind to - repressors, which can reduce the activity of RNA synthesis from this gene - in other words, reduce it expression.

Gene structure in prokaryotes

The general plan of gene structure in prokaryotes and eukaryotes is no different - both contain a regulatory region with a promoter and operator, a transcription unit with coding and untranslated sequences, and a terminator. However, the organization of genes in prokaryotes and eukaryotes is different.

Rice. 18. Scheme of gene structure in prokaryotes (bacteria) -the image is enlarged

At the beginning and end of the operon there are common regulatory regions for several structural genes. From the transcribed region of the operon, one mRNA molecule is read, which contains several coding sequences, each of which has its own start and stop codon. From each of these areas withone protein is synthesized. Thus, Several protein molecules are synthesized from one mRNA molecule.

Prokaryotes are characterized by the combination of several genes into a single functional unit - operon. The operation of the operon can be regulated by other genes, which can be noticeably distant from the operon itself - regulators. The protein translated from this gene is called repressor. It binds to the operator of the operon, regulating the expression of all genes contained in it at once.

Prokaryotes are also characterized by the phenomenon Transcription-translation interfaces.

Rice. 19 The phenomenon of coupling of transcription and translation in prokaryotes - the image is enlarged

Such coupling does not occur in eukaryotes due to the presence of a nuclear envelope that separates the cytoplasm, where translation occurs, from the genetic material on which transcription occurs. In prokaryotes, during RNA synthesis on a DNA template, a ribosome can immediately bind to the synthesized RNA molecule. Thus, translation begins even before transcription is completed. Moreover, several ribosomes can simultaneously bind to one RNA molecule, synthesizing several molecules of one protein at once.

Gene structure in eukaryotes

The genes and chromosomes of eukaryotes are very complexly organized

Many species of bacteria have only one chromosome, and in almost all cases there is one copy of each gene on each chromosome. Only a few genes, such as rRNA genes, are found in multiple copies. Genes and regulatory sequences make up virtually the entire prokaryotic genome. Moreover, almost every gene strictly corresponds to the amino acid sequence (or RNA sequence) it encodes (Fig. 14).

The structural and functional organization of eukaryotic genes is much more complex. The study of eukaryotic chromosomes, and later the sequencing of complete eukaryotic genome sequences, brought many surprises. Many, if not most, eukaryotic genes have an interesting feature: their nucleotide sequences contain one or more DNA sections that do not encode the amino acid sequence of the polypeptide product. Such untranslated insertions disrupt the direct correspondence between the nucleotide sequence of the gene and the amino acid sequence of the encoded polypeptide. These untranslated segments within genes are called introns, or built-in sequences, and the coding segments are exons. In prokaryotes, only a few genes contain introns.

So, in eukaryotes, the combination of genes into operons practically does not occur, and the coding sequence of a eukaryotic gene is most often divided into translated sections - exons, and untranslated sections - introns.

In most cases, the function of introns is not established. In general, only about 1.5% of human DNA is “coding,” that is, it carries information about proteins or RNA. However, taking into account large introns, it turns out that human DNA is 30% genes. Because genes make up a relatively small proportion of the human genome, a significant portion of DNA remains unaccounted for.

Rice. 16. Scheme of gene structure in eukaryotes - the image is enlarged

From each gene, immature or pre-RNA is first synthesized, which contains both introns and exons.

After this, the splicing process takes place, as a result of which the intronic regions are excised, and a mature mRNA is formed, from which protein can be synthesized.

Rice. 20. Alternative splicing process - the image is enlarged

This organization of genes allows, for example, when different forms of a protein can be synthesized from one gene, due to the fact that during splicing exons can be stitched together in different sequences.

Rice. 21. Differences in the structure of genes of prokaryotes and eukaryotes - the image is enlarged

MUTATIONS AND MUTAGENESIS

Mutation is called a persistent change in the genotype, that is, a change in the nucleotide sequence.

The process that leads to mutations is called mutagenesis, and the body All whose cells carry the same mutation - mutant.

Mutation theory was first formulated by Hugo de Vries in 1903. Its modern version includes the following provisions:

1. Mutations occur suddenly, spasmodically.

2. Mutations are passed on from generation to generation.

3. Mutations can be beneficial, harmful or neutral, dominant or recessive.

4. The probability of detecting mutations depends on the number of individuals studied.

5. Similar mutations can occur repeatedly.

6. Mutations are not directed.

Mutations can occur under the influence of various factors. There are mutations that arise under the influence of mutagenic impacts: physical (for example, ultraviolet or radiation), chemical (for example, colchicine or reactive oxygen species) and biological (for example, viruses). Mutations can also be caused replication errors.

Depending on the conditions under which mutations appear, mutations are divided into spontaneous- that is, mutations that arose under normal conditions, and induced- that is, mutations that arose under special conditions.

Mutations can occur not only in nuclear DNA, but also, for example, in mitochondrial or plastid DNA. Accordingly, we can distinguish nuclear And cytoplasmic mutations.

As a result of mutations, new alleles can often appear. If a mutant allele suppresses the action of a normal one, the mutation is called dominant. If a normal allele suppresses a mutant one, this mutation is called recessive. Most mutations that lead to the emergence of new alleles are recessive.

Mutations are distinguished by effect adaptive leading to increased adaptability of the organism to the environment, neutral, which do not affect survival, harmful, reducing the adaptability of organisms to environmental conditions and lethal, leading to the death of the organism in the early stages of development.

According to the consequences, mutations leading to loss of protein function, mutations leading to emergence protein has a new function, as well as mutations that change gene dosage, and, accordingly, the dose of protein synthesized from it.

A mutation can occur in any cell of the body. If a mutation occurs in a germ cell, it is called germinal(germinal or generative). Such mutations do not appear in the organism in which they appeared, but lead to the appearance of mutants in the offspring and are inherited, so they are important for genetics and evolution. If a mutation occurs in any other cell, it is called somatic. Such a mutation can manifest itself to one degree or another in the organism in which it arose, for example, leading to the formation of cancerous tumors. However, such a mutation is not inherited and does not affect descendants.

Mutations can affect regions of the genome of different sizes. Highlight genetic, chromosomal And genomic mutations.

Gene mutations

Mutations that occur on a scale smaller than one gene are called genetic, or point (point). Such mutations lead to changes in one or several nucleotides in the sequence. Among gene mutations there arereplacements, leading to the replacement of one nucleotide with another,deletions, leading to the loss of one of the nucleotides,insertions, leading to the addition of an extra nucleotide to the sequence.

Rice. 23. Gene (point) mutations

According to the mechanism of action on the protein, gene mutations are divided into:synonymous, which (as a result of the degeneracy of the genetic code) do not lead to a change in the amino acid composition of the protein product,missense mutations, which lead to the replacement of one amino acid with another and can affect the structure of the synthesized protein, although they are often insignificant,nonsense mutations, leading to the replacement of the coding codon with a stop codon,mutations leading to splicing disorder:

Rice. 24. Mutation patterns

Also, according to the mechanism of action on the protein, mutations are distinguished that lead to frame shift reading, such as insertions and deletions. Such mutations, like nonsense mutations, although they occur at one point in the gene, often affect the entire structure of the protein, which can lead to a complete change in its structure.

Rice. 29. Chromosome before and after duplication

Genomic mutations

Finally, genomic mutations affect the entire genome, that is, the number of chromosomes changes. There are polyploidies - an increase in the ploidy of the cell, and aneuploidies, that is, a change in the number of chromosomes, for example, trisomy (the presence of an additional homologue on one of the chromosomes) and monosomy (the absence of a homologue on the chromosome).

Video on DNA

DNA REPLICATION, RNA CODING, PROTEIN SYNTHESIS

What are DNA and RNA? What are their functions and significance in our world? What are they made of and how do they work? This and more is discussed in the article.

What are DNA and RNA

Biological sciences that study the principles of storage, implementation and transmission of genetic information, the structure and functions of irregular biopolymers belong to molecular biology.

Biopolymers, high-molecular organic compounds that are formed from nucleotide residues, are nucleic acids. They store information about a living organism, determine its development, growth, and heredity. These acids are involved in protein biosynthesis.

There are two types of nucleic acids found in nature:

• DNA - deoxyribonucleic;
• RNA is ribonucleic.

The world was told what DNA is in 1868, when it was discovered in the cell nuclei of leukocytes and salmon sperm. They were later found in all animal and plant cells, as well as in bacteria, viruses and fungi. In 1953, J. Watson and F. Crick, as a result of X-ray structural analysis, built a model consisting of two polymer chains that are twisted in a spiral around one another. In 1962, these scientists were awarded the Nobel Prize for their discovery.

Deoxyribonucleic acid

What is DNA? This is a nucleic acid that contains the genotype of an individual and transmits information by inheritance, self-reproducing. Because these molecules are so large, there are a huge number of possible nucleotide sequences. Therefore, the number of different molecules is virtually infinite.

DNA structure

These are the largest biological molecules. Their size ranges from one quarter in bacteria to forty millimeters in human DNA, much larger than the maximum size of a protein. They consist of four monomers, the structural components of nucleic acids - nucleotides, which include a nitrogenous base, a phosphoric acid residue and deoxyribose.

Nitrogen bases have a double ring of carbon and nitrogen - purines, and one ring - pyrimidines.

Purines are adenine and guanine, and pyrimidines are thymine and cytosine. They are designated by capital Latin letters: A, G, T, C; and in Russian literature - in Cyrillic: A, G, T, Ts. Using a chemical hydrogen bond, they connect with each other, resulting in the appearance of nucleic acids.

In the Universe, the spiral is the most common shape. So the structure of the DNA molecule also has it. The polynucleotide chain is twisted like a spiral staircase.

The chains in the molecule are directed oppositely from each other. It turns out that if in one chain the orientation is from the 3" end to the 5", then in the other chain the orientation will be the opposite - from the 5" end to the 3".

Principle of complementarity

The two strands are joined into a molecule by nitrogenous bases in such a way that adenine has a bond with thymine, and guanine has only a bond with cytosine. Consecutive nucleotides in one chain determine the other. This correspondence, which underlies the appearance of new molecules as a result of replication or duplication, has come to be called complementarity.

It turns out that the number of adenyl nucleotides is equal to the number of thymidyl nucleotides, and guanyl nucleotides are equal to the number of cytidyl nucleotides. This correspondence became known as Chargaff's rule.

Replication

The process of self-reproduction, which occurs under the control of enzymes, is the main property of DNA.

It all starts with the unwinding of the helix thanks to the enzyme DNA polymerase. After the hydrogen bonds are broken, a daughter chain is synthesized in one and the other strand, the material for which is the free nucleotides present in the nucleus.

Each DNA strand is a template for a new strand. As a result, two absolutely identical parent molecules are obtained from one. In this case, one thread is synthesized as a continuous thread, and the other is first fragmentary, only then joining.

DNA genes

The molecule carries all the important information about nucleotides and determines the location of amino acids in proteins. The DNA of humans and all other organisms stores information about its properties, passing them on to descendants.

Part of it is a gene - a group of nucleotides that encodes information about a protein. The totality of a cell's genes forms its genotype or genome.

Genes are located on a specific section of DNA. They consist of a certain number of nucleotides that are arranged in a sequential combination. This means that the gene cannot change its place in the molecule, and it has a very specific number of nucleotides. Their sequence is unique. For example, one order is used for producing adrenaline, and another for insulin.

In addition to genes, DNA contains non-coding sequences. They regulate gene function, help chromosomes, and mark the beginning and end of a gene. But today the role of most of them remains unknown.

Ribonucleic acid

This molecule is similar in many ways to deoxyribonucleic acid. However, it is not as large as DNA. And RNA also consists of four types of polymeric nucleotides. Three of them are similar to DNA, but instead of thymine it contains uracil (U or U). In addition, RNA consists of a carbohydrate - ribose. The main difference is that the helix of this molecule is single, unlike the double helix in DNA.

Functions of RNA

The functions of ribonucleic acid are based on three different types of RNA.

Information transfers genetic information from DNA to the cytoplasm of the nucleus. It is also called matrix. This is an open chain synthesized in the nucleus using the enzyme RNA polymerase. Despite the fact that its percentage in the molecule is extremely low (from three to five percent of the cell), it has the most important function - to act as a matrix for the synthesis of proteins, informing about their structure from DNA molecules. One protein is encoded by one specific DNA, so their numerical value is equal.

The ribosomal system mainly consists of cytoplasmic granules - ribosomes. R-RNAs are synthesized in the nucleus. They account for approximately eighty percent of the entire cell. This species has a complex structure, forming loops on complementary parts, which leads to molecular self-organization into a complex body. Among them, there are three types in prokaryotes, and four in eukaryotes.

The transport acts as an “adapter”, arranging the amino acids of the polypeptide chain in the appropriate order. On average, it consists of eighty nucleotides. The cell contains, as a rule, almost fifteen percent. It is designed to transport amino acids to where protein is synthesized. There are from twenty to sixty types of transfer RNA in a cell. They all have a similar organization in space. They acquire a structure called a cloverleaf.

Meaning of RNA and DNA

When DNA was discovered, its role was not so obvious. Even today, although much more information has been revealed, some questions remain unanswered. And some may not even be formulated yet.

The well-known biological significance of DNA and RNA is that DNA transmits hereditary information, and RNA is involved in protein synthesis and encodes protein structure.

However, there are versions that this molecule is connected with our spiritual life. What is human DNA in this sense? It contains all the information about him, his life activity and heredity. Metaphysicians believe that the experience of past lives, the restoration functions of DNA, and even the energy of the Higher Self - the Creator, God, is contained in it.

In their opinion, the chains contain codes relating to all aspects of life, including the spiritual part. But some information, for example about restoring one's body, is located in the structure of the crystal of multidimensional space located around DNA. It represents a dodecahedron and is the memory of all life force.

Due to the fact that a person does not burden himself with spiritual knowledge, the exchange of information in DNA with the crystalline shell occurs very slowly. For the average person it is only fifteen percent.

It is assumed that this was done specifically to shorten human life and fall to the level of duality. Thus, a person’s karmic debt increases, and the level of vibration necessary for some entities is maintained on the planet.

06.04.2015 13.10.2015

All life forms are engaged in construction and contact with each other. Initially, both of these processes occur in all cells. DNA does the construction, and RNA does the contacting. The first objective information about them appeared about 50-60 years ago. But, despite all the achievements of their research, scientists’ knowledge of macromolecules is still by no means complete.

History of discovery

The isolation of the substance and the structure of DNA was carried out by I.F. Mischer back in 1868 from the residual elements of cells that were contained in the composition of pus. The chemical substance was first called nuclein. And after the scientist established that the composition of the macromolecule contains acidic features, the substance began to be called nucleic acid. It is now called deoxyribonucleic acid. Little by little, scientists have proven that it is not proteins, but precisely the macromolecule under study, that is the carrier of various genetic information.
The importance of RNA in protein synthesis was suggested back in 1939 by T.O. Kaspersson, J. Brachet and D. Schultz. Subsequently, D. Mairbucks isolated the matrix of the first macromolecule, which encoded rabbit hemoglobin, showing in the form of a table that when it is sent to the oocytes, an identical protein substance is created.
The year 1953 was marked by a new stage in the study of the structure of the molecule. Scientists, through identifying its structural features and composition, contributed to the emergence of molecular biological science.

Description

After the birth of the new biological, its main postulate was expressed: DNA-RNA-protein. In other words, the information contained in the gene substance is carried out as proteins, but not directly, but through a similar base of the RNA polymer. As a result, DNA carries out synthesis on DNA, guaranteeing its own reduplication process, that is, the original genetic matter is reproduced. In comparison, RNA synthesizes based on the nitrogenous structure of DNA and rewrites genetic information as multiple RNA duplicates.

The nitrogenous bases of the RNA molecule are matrix structures for the protein synthesis process - information about genetics is transmitted by polypeptide chains, which can be described in the form of a table. At the same time, a clear impression appears of the significantly more diverse capabilities of this macromolecule compared to the composition of DNA, which exists, as a rule, only with the need to preserve and transmit the traits of heredity.
The presented macromolecules differ in their composition and the length of the polymer chain; this information is displayed in all tables on genetics. The composition of the longest DNA macromolecule in human cells is 250 million. nitrogenous bases - monomers, and its length is more than 8 centimeters. Thus, to express the order of DNA nucleotides of one human cell, more than 800 thousand text pages in the form of tables will be needed.

Use in medicine and science

DNA bases are the most optimal carriers of various information on the planet. Despite the fact that the first examples of storing digital tables by macromolecules appeared about thirty years ago, only a few years ago Harvard scientists were able to reliably reveal their composition and code. They were able to store about 700 terabytes of information from 1 gram of macromolecule. This is equivalent to approximately 150 kg of computer hard drives, and in the form of a macromolecule it is only a droplet.
Thanks to current technologies, it is possible to read the structure of a macromolecule in a few hours, but this is very expensive.
Job. Therefore, as a rule, from a practical point of view, the possibilities of this form of storing information are quite limited. But the very idea that all of humanity's knowledge about the world could be preserved in a space that is no larger than the size of a refrigerator is simply amazing and haunts scientists.
The importance of the study and application of RNA bases was confirmed by the Nobel Medical Prize, which S. Ochoa received in 1959 for discovering the mechanism of RNA synthesis. In 1965, in the laboratory of R. Holey, the order of the 77 nucleotide substances of one of the tRNAs of the yeast S.cerevisiae was established. For this discovery he was also awarded the Nobel Medical Prize in 1968.
In 1976, W. Faers, together with specialists from the Belgian University of Ghent, identified the first order and composition of the genome of the RNA-containing bacteriophage virus MS 2. In the early 1990s. It was found that when foreign genes are introduced into the plant genome, this leads to the suppression of the structure of similar plant genes.

Today there are many different situations where the unique features of the presented macromolecules are manifested. In particular, scientists learned that due to a significant surge of radiation released into the atmosphere, the DNA of all citizens born after 1955 contains small particles of carbon-fourteen.

Interestingly, an individual can be endowed with two sets of DNA bases. Thus, many cases of pregnancies begin in such a way that often one of the twins absorbs the other even before the embryo is discovered. In 99 percent of phenomena, this is where everything ends, and many people live without knowing that they are one of the examples of chimerism. But under certain circumstances, if a twin has “absorbed” its own twin, then it may contain 2 different sets of macromolecules. This is often determined during compatibility studies, when it is necessary to transplant an organ from one person to another.
The ability of DNA cells to express themselves can be clearly demonstrated by silkworms. Thanks to the macromolecule, the cell is able to recreate any number of RNAs. Thus, a single DNA gene is capable of forming approximately 1 thousand RNA duplicates, each of which can transmit information to form a huge number of silk thread protein substances. Today, this is the most representative example of the construction and contact of two macromolecules, which allows people to feel comfortable in light clothing. As a rule, in just 4 days, the genes of a single cell are capable of producing a billion protein substances.