What kinds of bases are there?

There are 8 bases: guanine (G), adenine (A), thymine (T, DNA specificity), uracil (U, RNA specificity), 5- cytosine methyl, 5- hydroxymethylcytosine (5-hmC), 5- cytosine formyl (5- cytosine), 5- cytosine carboxyl (5- cytosine carboxyl).

In the latest research results, the researchers found the seventh and eighth DNA bases: 5- formylcytosine and 5- carboxycytosine. These two bases are actually formed by the modification of cytosine by Tet protein, which is the key protein that Professor Zhang Yi's research group has been studying.

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In deoxyribonucleic acid and ribonucleic acid, the matching part is nitrogenous bases. These five bases are heterocyclic compounds, and the nitrogen atom is located on the ring or substituted amino group, and some of them (substituted amino group, purine ring 1 nitrogen and pyrimidine ring 3-nitrogen) directly participate in base pairing.

Adenine and guanine belong to purine family (abbreviated as R), and they have a bicyclic structure. Cytosine, uracil and thymine belong to pyrimidine family (Y), and their ring systems are six-membered heterocyclic rings.

A compound formed by covalent bond between a base and the carbon atom at 1 position of ribose or deoxyribose is called nucleoside. Nucleoside combines with phosphoric acid to form nucleotide, and the phosphoric acid group is connected to the fifth carbon atom of pentose.

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