first information about the chemical properties of deoxyribonucleic acid date back to 1868 year.In the 20th century, to the beginning of the forties, it was shown that the molecule is a linear polymer.As nucleotides are the monomeric units, which consist of a nitrogenous base, a pentose and a phosphate group (a five-carbon sugar).
Deoxyribonucleic acid may have a base of two types: a pyrimidine (thymine (T) and cytosine (C)) and a purine (adenine (A) and guanine (G)).The compound made using nucleotide phosphodiester bond.
biologists Crick and Watson in 1953, based on X-ray crystal analysis of DNA, we concluded that the native molecule consists of a pair of polymer chains that form a double helix.Polynucleotide strand wound on each other, are held together by hydrogen bonds that form between complementary (mutually corresponding) bases in opposite chains.When this pair formed only as follows: adenine-thymine, guanine-cytosine.Stabilization of the first in two, and the second pair - three hydrogen bonds.
double-stranded deoxyribonucleic acid has a length calculated as the number of pairs of mutually corresponding nucleotides (bp).For those molecules that are made up of millions and thousands of couples taken m.n.p. unitand kb, respectively.Thus, deoxyribonucleic acid, consists of a single human chromosome double helix.Its length is 263 m.p.n.
DNA denaturation (melting) is the process whereby a regular double helix linear molecule enters the coiled state.Upon melting of double-molecule splits into separate circuit.It is the temperature at which half of Deoxyribonucleic acid melted, a melting point.It depends on the quality of the molecular composition.
As mentioned above, a pair of G-C stabilized by three, and a pair of A-T - two hydrogen bonds.Accordingly, the higher the proportion of the first pair, the more stable the molecule.When denaturation of wavelength 260 nm, absorption of light increases.This hyperchromic effect makes it possible to maintain control over the state of the secondary molecular structure.If the solution is slowly cooled molten acid, then again between complementary strands can form weak bonds may spiral structure identical to the native (original).This ability of DNA to denaturation, annealing and hybridization method based molecules.It is used in the study of the structure of nucleic acids.
double-molecule being a carrier of genetic data, must comply with two major requirements.Firstly, it should be replicated (reproduced) with high accuracy, and secondly, to encode the synthesis of protein molecules.Deoxyribonucleic acid, a model which has been described by Crick and Watson, fully complies with these requirements.It is found that, in accordance with the principle of complementarity, each chain in the molecule can be the matrix for the formation of the new chain are mutually corresponding.As a result, one stage of replication thus occurs pair daughter molecules having a nucleotide sequence identical to that in the original DNA molecule.Moreover, this chain structural gene sets in the encoded protein amino acid sequence.
From the moment it was made public the discovery of DNA and the principle of complementarity, established processes, which are responsible for decoding genetic information and gene regulation in the synthesis of substances.In addition, the theory was developed and recombinant molecules.
