What is a genetic code: general information
In any cell and body, all the featuresanatomical, morphological and functional character are determined by the structure of proteins that enter into them. Hereditary property of the organism is the ability to synthesize certain proteins. In the DNA molecule, amino acids are located in the polypeptide chain, on which biological signs depend.
Each cell has its ownsequence of nucleotides in the polynucleotide chain of DNA. This is the genetic code of DNA. Through it, information on the synthesis of certain proteins is recorded. About what the genetic code, about its properties and genetic information is told in this article.
A bit of history
The idea that, perhaps, the genetic codeexists, was formulated by J. Gamow and A. Daun in the middle of the twentieth century. They described that the nucleotide sequence responsible for the synthesis of a particular amino acid contains at least three links. Later, we proved the exact number of three nucleotides (this is a unit of the genetic code), which was called a triplet or codon. A total of sixty-four nucleotides, because the molecules of acids where the protein or RNA synthesis occurs, consists of the residues of four different nucleotides.
What is the genetic code
The method for encoding a sequence of amino acid proteins due to the nucleotide sequence is characteristic of all living cells and organisms. That's what the genetic code is.
There are four nucleotides in DNA:
- adenine - A;
- thymine - T.
They are denoted by capital letters in Latin or (in Russian-language literature) by Russians.
RNA also contains four nucleotides, but one of them differs from DNA:
- adenine - A;
- uracil - U.
All nucleotides are aligned in chains, with a double helix 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.
Properties of the genetic code
The triplet. The unit of the genetic code consists of three letters, it is a triplet. This means that the twenty existing amino acids are ciphered by three specific nucleotides, which are called codons or trilpets. There are sixty-four combinations that can be created from four nucleotides. This number 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.
Uniqueness. One codon encrypts one amino acid. For example, in a healthy person's gene with information about the hemoglobin beta target, a triplet of GAG and GAA encodes glutamic acid. And for all who are sick with 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, thatmeans that it does not have "punctuation marks". That is, starting at a certain 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 somehow else.
Versatility. It is unique for all terrestrial organisms, from humans to fish, fungi and bacteria.
In the presented table there are not allavailable amino acids. Hydroxyproline, hydroxylizine, phosphoserine, iodo derivatives of tyrosine, cystine and some others are absent, since they are derivatives of other amino acids encoded by mRNA and formed after modification of proteins as a result of translation.
From the properties of the genetic code, it is known that onea codon is capable of encoding one amino acid. An exception is performing additional functions and encoding valine and methionine, a genetic code. The mRNA, being in the beginning with the codon, attaches tRNA, which carries formylmethion. Upon completion of the synthesis, it cleaves itself and captures the formyl residue behind it, converting it to a methionine residue. Thus, the aforementioned codons are the initiators of the synthesis of a chain of polypeptides. If they are not at the beginning, then they are no different from the others.
By this concept is meant a program of properties, which is transmitted from ancestors. It is inherent in geneticity as a genetic code.
The genetic code of RNA (ribonucleic acids) is realized during protein synthesis:
- transport tRNA;
- ribosomal p-RNA.
The information is transmitted by a direct link (DNA-RNA-protein) and reverse (medium-protein-DNA).
Organisms can receive, store, transmit it and use it most efficiently.
Passing by heredity, information determinesthe development of this or that organism. But because of interaction with the environment, the reaction of the latter is distorted, which is why evolution and development take place. Thus, new information is put in the body.
Calculation of the laws of molecular biologyand the discovery of the genetic code illustrated that it is necessary to combine genetics with Darwin's theory, on the basis of which a synthetic theory of evolution emerged - nonclassical biology.
Heredity, variability and naturalThe selection of Darwin is complemented by genetically determined selection. Evolution is realized at the genetic level through random mutations and by inheriting the most valuable traits that are most adapted to the environment.
Decoding of the code in humans
In the nineties the Human Genome project was launched,as a result of which genome fragments containing 99.99% of human genes were discovered in the 2000th genome. The fragments that are not involved in the synthesis of proteins and are not coded remain unknown. Their role remains unknown.
The role of such studies can not be overestimated.When they discovered what a genetic code is, it became known, according to what laws develops, how the morphological structure, the psyche, the predisposition to certain diseases, the metabolism and the vices of individuals are formed.