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What is nucleic acid?

Nucleic acid is another important life form, which was discovered 30 years later than protein. 1869, the young Swiss scientist Michelle hydrolyzed pus cells obtained from surgical bandages with pepsin, and found that this enzyme could not decompose the nucleus, and the nucleus shrank a little, but remained intact. After laboratory analysis, Michelle found that the nucleus is mainly composed of a substance containing phosphorus, and its properties are completely different from those of protein. He called this substance "nucleoplasm" and soon discovered that "nucleoplasm" was acidic, hence the name "nucleic acid". In the mid-1950s, biochemists found that the molecular weight of nucleic acid was as high as 6 million, which showed that the molecular weight of nucleic acid was indeed as big as that of protein, or even larger.

German chemist Wigan discovered the position of nucleic acid in cells by staining: DNA is located in the nucleus, especially in chromosomes; There is DNA in the cells of animals and plants, but the cell content of different species is different, and nucleic acid is a more necessary living body, which is confirmed by genetics. We also know that viruses containing only nucleic acids can infect parasitic cells and produce complete progeny viruses including nucleic acids and protein. In recent years, a tiny life form gray virus is a nucleic acid molecule composed of only a few hundred nucleotides. It can be seen that the study of nucleic acid is of fundamental significance to the study of life phenomena.

Nucleic acid consists of simpler nucleotides, which can be decomposed into nucleotides containing purine (or pyrimidine), ribose (or deoxyribose) and phosphoric acid.

Nucleotides are mainly composed of four different bases. Alkali is a derivative of purine, which is a nitrogen-containing heterocyclic compound and is called alkali because of its alkalinity. The salt bases in nucleotides are adenine, guanine, cytosine and thymine.

The sugar contained in nucleotide is not six-carbon sugar, but five-carbon sugar, which is called ribose. Because of the different properties of pentasaccharide contained in nucleic acid, two different nucleic acids are formed. Yeast nucleic acid contains "ribose", called "ribonucleic acid" (RNA); The sugar in thymic acid is very similar. Sugar has only one atom, so it is called "DNA"

In the 1940s, biochemists found that the number of protein and RNA in chromosomes can be completely different, but the number of DNA is always the same, which shows that DNA is closely related to genes. Modern biologists have proved that DNA plays the role of gene and is genetic material. After Dino discovered potato spindle virus in 1967, it was a virus-like virus with only nucleic acid and no protein, and seven virus-like viruses with only nucleic acid and no protein were discovered one after another, which proved that life existed in the form of nucleic acid.

With the research on the structure and function of RNA and DNA molecules, the birth of molecular biology, the discovery of genetic code and the establishment of genetic engineering, the exploration of the mystery of life is getting deeper and deeper, and human beings, animals, microorganisms and viruses (non-cell organisms) are unified at the level of nucleic acid molecules.

However, it is possible that nucleic acids are not necessary to produce viral effects. 1967 found that sheep itch was caused by particles smaller than poison. This subclass has no nucleic acid, but it can be formed by changing the function of cell genes. This has attracted some sciences to embark on a new journey to further explore the mysteries of life.