Functions of DNA and its structure
At the core of the vital activity of living cellsorganisms are the functions of biological polymers: nucleic acids, carbohydrates, proteins and lipids. Biopolymers consist of monomers, hydrocarbon structures, which also include nitrogen, oxygen, sulfur and phosphorus.
In the 19th century, a study was begun of the structure of substances that make up a living cell, but the functions of DNA, proteins, RNA and their structure were finally determined in the 20th century.
Friedrich Mischer in 1868 isolated from the nuclei of cellsleukocytes phosphorus-containing substance and called it a nuclein. Then Richard Altman in 1889 determined that this substance consists of a special acid and protein. It was then that they first heard about the term "nucleic acid". However, until the function of nucleic acids was established, it was still far off.
DNA-deoxyribonucleic acids areThe largest biological polymers, consisting of hundreds of monomers - deoxyribonucleotides. In their composition, in addition to sugar (deoxyribose), there are 4 types of nucleotides: adenine - A, thymidine - T, cytosine - C, guanine - G.
The first time DNA was considered a nucleic acidanimal origin, because it was isolated from the thymus of animals, and RNA, isolated from wheat seedlings - plant. It was believed that the biochemical difference between the cells of the racesshadows and animals. However, in the middle of the twentieth century, RNA and DNA were found to be part of all cells.
Directly the structure of nucleic acids began to study Erwin Chargaff, who in 1953 found out that the nucleotides that are part of the same acids form pairs with a strict pattern.
One pyrimidine and one purine base always enter into the bond, T = C, A = T. That is, adenine binds to thymidine and guanine to cytosine.
And for the DNA function it is essential that the connection in the first case is provided by 2 hydrogen pairs, and in the second - by three.
The rule of Chargaff turned out to be the basis on which Watson and Crick constructed the structure of a double helix of DNA.
In this molecule, as in protein molecules, the primary, secondary and tertiary structures are different.
The primary structure is a linear sequence of monomers in one chain.
Of course, in nature, DNA does not occur in the form of a single chain, but here we are talking about the primary structure of the biopolymer, which determines all its properties.
The secondary structure is spatialcharacteristic of a biopolymer. In the case of DNA, it is two polynucleotide chains, each of which is twisted in a spiral to the right, and both are simultaneously twisted clockwise around the common axis. These chains are held together by hydrogen bonding forces. The tertiary structure of DNA is determined by further spiralization of the molecule.
A giant step forward was made with the discoveryThe fact that the functions of DNA consist in the transfer and storage of genetic information. DNA contains a hereditary program about the structure of proteins specific for each organism. Together with RNA molecules, they transmit hereditary information from the body to the body. The function of DNA also includes the implementation of genetic information. They participate in the processes of transcription, replication and translation, thus ensuring the synthesis of a variety of proteins.