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'Nucleobases' are the parts of RNA and DNA that may be involved in pairing (see also base pairs). These include cytosine, guanine, adenine, thymine (DNA), uracil (RNA) and xanthine and hypoxanthine (mutated forms of guanine and adenine, respectively). These are abbreviated as C, G, A, T, U, X and HX respectively. They are usually simply called 'bases' in genetics. Because A, G, C and T appear in the DNA, these molecules are called 'DNA-bases'; A, G, C and U are called 'RNA-bases', respectively.
Hypoxanthine and xanthine are created through mutagen presence, through deamination (replacement of the amine-group with a hydroxyl-group). Hypoxanthine is produced from adenine, xanthine from guanine and uracil from cytosine.
Uracil replaces thymine in RNA. These two bases are identical except that uracil lacks the 5' methyl group. Adenine and guanine belong to the double-ringed class of molecules called purines (abbreviated as R). Cytosine, thymine, and uracil are all pyrimidines (abbreviated as Y).
A base covalently bound to the 1' carbon of a ribose or deoxyribose is called a ''nucleoside'', and a nucleoside with one or more phosphate groups attached at the 5' carbon is called a ''nucleotide''.

Contents

Structure

Purines

Pyrimidines

See also

External links

Structure

★ The "skeleton" of adenine, guanin, hypoxanthine and xanthine is purine, hence the name 'purine-bases'.

★ The "skeleton" of cytosine, uracil and thymine is pyrimidine, hence 'pyrimidine-bases'.

Purines

Nucleobase	Nucleoside
Chemical structure of adenine Adenine	Chemical structure of adenosine Adenosine A
Chemical structure of guanine Guanine	Chemical structure of guanosine Guanosine G
Chemical structure of hypoxanthine Hypoxanthine	Chemical structure of hypoxanthinosine Hypoxanthinosine HX
Chemical structure of xanthine Xanthine	Chemical structure of xanthinosine Xanthinosine X

Pyrimidines

Nucleobase	Nucleoside
Chemical structure of thymine Thymine	Chemical structure of thymidine Thymidine T
Chemical structure of cytosine Cytosine	Chemical structure of cytidine Cytidine C
Chemical structure of uracil Uracil	Chemical structure of uridine Uridine U

See also

★ Nucleoside

★ Nucleotide

★ DNA

★ RNA

External links

★ Base pairing in DNA Double Helix (shows specific hydrogen bonds)