In any cell and body, all the features of the anatomical, morphological and functional nature are determined by the structure of the proteins that enter them. The hereditary property of the body is the ability to synthesize certain proteins. In a DNA molecule, amino acids are located in a polypeptide chain, on which biological characters depend.
Each cell is characterized by its own sequence of nucleotides in the polynucleotide DNA chain. This is the genetic code of DNA. Through it, information is recorded on the synthesis of certain proteins. What is the genetic code, about its properties and genetic information is described in this article.
A bit of history
The idea that perhaps a genetic code exists was formulated by J. Gamow and A. Down in the mid-twentieth century. They described that the nucleotide sequence responsible for the synthesis of a particular amino acid contains at least three units. Later they proved the exact number of three nucleotides (this is a unit of the genetic code), which was called a triplet or codon. There are sixty-four nucleotides in total, because the acid molecule where the synthesis of the protein or RNA occurs consists of the residues of four different nucleotides.
What is a genetic code?
A method of encoding an amino acid protein sequence due to a nucleotide sequence is characteristic of all living cells and organisms. This is what the genetic code is.
There are four nucleotides in DNA:
- adenine - A;
- guanine - G;
- cytosine - C;
- thymine - T.
They are indicated in capital letters Latin or (in Russian literature) Russian.
Four nucleotides are also present in RNA, however one of them is different from DNA:
- adenine - A;
- guanine - G;
- cytosine - C;
- uracil - U.
All nucleotides are arranged in chains, moreover, a double helix is obtained in DNA, and a single helix in RNA.
Proteins are built on twenty amino acids, where they, located in a certain sequence, determine its biological properties.
Genetic Code Properties
Tripletness. The unit of the genetic code consists of three letters, it is triplet. This means that twenty existing amino acids are encrypted with three specific nucleotides called codons or trilpets. There are sixty-four combinations that can be created from four nucleotides. This amount is more than enough to encode twenty amino acids.
Degeneracy. Each amino acid corresponds to more than one codon, with the exception of methionine and tryptophan.
Unambiguity. One codon encrypts one amino acid. For example, in the gene for a healthy person with information about the beta target of hemoglobin, the triplet GAG and GAA encodes glutamic acid. And for everyone who has sickle cell anemia, one nucleotide is replaced.
Collinearity. The amino acid sequence always corresponds to the nucleotide sequence that the gene contains.
The genetic code is continuous and compact, which means that it does not have “punctuation marks”. That is, starting at a specific codon, there is a continuous reading. For example, AUGGUGTSUUAAUGUG will be read as: AUG, GUG, TSUU, AAU, GUG. But not AUG, UGG, and so on or otherwise.
Universality. It is absolutely unique for all terrestrial organisms, from humans to fish, fungi and bacteria.
Table
Not all amino acids are present in the table below. Hydroxyproline, hydroxylisine, phosphoserine, tyrosine iodo derivatives, cystine and some others are absent, as they are derivatives of other amino acids encoded by mRNA and formed after protein modification as a result of translation.
From the properties of the genetic code, it is known that one codon is able to encode one amino acid. An exception is that it performs additional functions and encodes valine and methionine, the genetic code. IRNK, being at the beginning with the codon, attaches t-RNA, which carries formylmethion. Upon completion of the synthesis, it cleaves itself and captures the formyl residue, transforming into the methionine residue. So, the above codons are the initiators of the synthesis of the chain of polypeptides. If they are not at the beginning, then they are no different from others.
Genetic information
By this concept is meant a property program that is passed from ancestors. It is embedded in heredity as a genetic code.
The genetic code of RNA (ribonucleic acids) is realized during protein synthesis:
- informational i-RNA;
- transport t-RNA ;
- ribosomal r-RNA.
Information is transmitted by direct communication (DNA-RNA-protein) and feedback (medium-protein-DNA).
Organisms can receive, preserve, transmit it and use it most effectively.
Passed by inheritance, information determines the development of an organism. But due to the interaction with the environment, the reaction of the latter is distorted, due to which evolution and development take place. Thus, new information is laid in the body.
The calculation of the laws of molecular biology and the discovery of the genetic code have illustrated that it is necessary to combine genetics with Darwin's theory, on the basis of which a synthetic theory of evolution appeared - non-classical biology.
Darwin’s heredity, variability, and natural selection are complemented by genetically determined selection. Evolution is realized at the genetic level through random mutations and the inheritance of the most valuable traits that are most adapted to the environment.
Decryption of the code in humans
In the nineties, the Human Genome project was launched, as a result of which fragments of the genome containing 99.99% of human genes were discovered in the 2000s. Fragments that are not involved in protein synthesis and are not encoded remain unknown. Their role is still unknown.
The last chromosome 1 discovered in 2006 is the longest in the genome. More than three hundred and fifty diseases, including cancer, result from violations and mutations in it.
The role of such studies is difficult to overestimate. When they discovered what the genetic code is, it became known by what patterns development occurs, how the morphological structure, psyche, predisposition to certain diseases, metabolism and vices of individuals are formed.