The universal genetic code

The genetic code is a special cipher of hereditary information with the help of nucleic acid molecules . Based on this encoded information, genes appropriately control the synthesis of proteins and enzymes in the body, thereby determining the metabolism. In turn, the structure of individual proteins and their functions is determined by the location and composition of amino acids - the structural units of the protein molecule.

In the middle of the last century, genes were identified, which are separate sites of deoxyribonucleic acid (abbreviated - DNA). The nucleotide links form a characteristic double chain in DNA molecules assembled in the form of a spiral.

Scientists have found a connection between the genes and the chemical structure of individual proteins, the essence of which is that the structural order of the arrangement of amino acids in protein molecules completely corresponds to the order of nucleotides in the gene. Having established this connection, scientists decided to decipher the genetic code, i.e. Establish the laws of the correspondence of the structural orders of nucleotides to DNA and amino acids in proteins.

There are only four types of nucleotides:

1) A - adenyl;

2) Г - guanyl;

3) T - thymidyl;

4) C - cytidyl.

The composition of proteins includes twenty kinds of basic amino acids. With the deciphering of the genetic code, difficulties arose, since the nucleotides are much smaller than the amino acid. When solving this problem, it was suggested that the amino acids are encoded by various combinations of three nucleotides (the so-called codon or triplet).

If we count all possible combinations, then such triplets will be 64, that is, three times more than amino acids - an excess of triplets is obtained.

In addition, it was necessary to explain how the triplets along the gene are located. So there were three main groups of theories:

1) triplets follow one after the other continuously, i.e. Form a solid code;

2) triplets are arranged with an alternation of "meaningless" areas, i.e. So-called "commas" and "paragraphs" are formed in the code;

3) triplets can overlap, i. E. The end of the first triplet can form the beginning of the next.

At the present time, the theory of code continuity is mainly used.

The genetic code and its properties

1) The triplet code - it consists of arbitrary combinations of three nucleotides that form codons.

2) The genetic code is redundant - this is the consequence of its tripletness. One amino acid can be encoded by several codons, since codons, according to mathematical calculations, are three times more than amino acids. Some codons perform certain terminating functions: some can be "stop signals" that program the end of the production of the amino acid chain, while others can designate the initiation of code reading.

3) The genetic code is unique - only one amino acid can correspond to each of the codons.

4) The genetic code has collinearity, i.e. The sequence of nucleotides and the sequence of amino acids clearly correspond to each other.

5) The code is written continuously and compactly, there are no "nonsense" nucleotides in it. It starts with a certain triplet, which is replaced by the next without a break and ends with a stop codon.

6) The genetic code has a universality - the genes of any organism encode information about proteins in exactly the same way. It does not depend on the level of complexity of the organization of the organism or its systemic position.

Modern science suggests that the genetic code arises directly when a new organism is born from bone matter. Random changes and evolution processes make possible any code options, i.e. Amino acids can be rearranged in any sequence. Why did this type of code survive during evolution, why is the code universal and has a similar structure? The more science learns about the phenomenon of the genetic code, the more new mysteries arise.