existence of living matter related to the presence of nucleic acids.F. Miescher first isolated these substances from the nuclei of white blood cells (1869).Later they were found in all the cells of living organisms (people, animals, plants, bacteria and viruses).
nucleic acids - prostatic group nucleoprotein.In the hydrolysis of nucleic acids is obtained nitrogenous bases (adenine, cytosine, guanine, uracil and thymine), pentose (deoxyribose, ribose), and acid phosphate.Given the biochemical composition, the nucleic acids are classified into deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).The structure of human DNA includes deoxyribose in RNA structure - ribose.These acids differ in molecular structure, the composition of the nitrogenous bases, cellular localization, and of course, functions.Biosoedineniya molecule which consists of a purine or pyrimidine base and monosaccharide (ribose or deoxyribose) are called nucleosides.Title nucleoside determined nitrogenous base, which is contained in it.Thus, a nucleoside, which includes the structure of adenine molecule is called adenosine, thymine - thymidine, uracil - uridine, cytosine - cytidine, guanine - guanosine.Depending on monosaccharides (pentoses), which are part of the molecules distinguish ribonucleosides and deoxyribonucleosides.
human DNA - the chemical basis of genes, which are concentrated hereditary information of an organism.It is localized primarily in the nucleus of cells, preferably in the chromosomes.During hydrolysis of DNA nucleotides are formed: dezoksiadenilovaya (A) dezoksiguanilovaya (T) dezoksitsitidilovaya (U) and thymidylic (T) acids.Sometimes consisting of nucleotides found in small quantities other derivatives of purines and pyrimidines - minor base: 5-oksimetiltsitozin (in bacteriophage), 5-methylcytosine (in the tissues of the thymus), and others.Nucleotides are connected in a polynucleotide chain (DNA) oxygen bridges formed by hydroxyl - acid residues of phosphate of one nucleotide and the hydroxyl group at the third carbon atom of the second residue deoxyribose nucleotides.
placement sequence of nucleotides in human DNA by sequencing study (English. Seguence - study of the sequence).To do this, use the sequencer device, which is based on computer analysis of the sequence sets the placement of nucleotides (up to a hundred units).
number of nucleotides in the molecule of human DNA is 25 000 - 35 000 or more, and the molecular weight - from several million to 2-5 billion. The DNA molecules can be "seen" under the electron microscope.The absolute amount of the four types of nucleotides (A, G, C and T) in the DNA molecules of different origin varies over a wide range.
primary structure of DNA
Crick and Watson D. in 1953 found that the deoxyribonucleic acid molecule is a double helix polynucleotide chains twisted around its axis.Helix resembles a spiral staircase, which formed handrails deoxyribose residues interconnected by phosphate-ester bonds by type 3 - 5, and the stage - nitrogen bases.Adenine is connected by hydrogen bonds with thymine, guanine - with cytosine.Configuration deoxyribonucleic acid may be compressed and stretched.This is the secondary structure of DNA.Some bacteriophages found single- DNA molecule.For a molecule of deoxyribonucleic acid characteristic of the tertiary structure, which is formed as a result of reunification and double-stranded ring-shaped DNA, and subsequent formation of spiralizirovannyh superspiralizirovannyh structures.
