Nucleotide

A nucleotide is a monomer or the structural unit of nucleotide chains forming nucleic acids as RNA and DNA. A nucleotide consists of a heterocyclic nucleobase, a pentose sugar, and a phosphate or polyphosphate group. Nucleotides also play important roles in cellular energy transport and transformations (notably ATP and NAD+/NADH), and in enzyme regulation (see for example, protein kinase).

The nucleobase can be a purines or pyrimidines, the sugar can be deoxyribose in DNA or ribose in RNA, and the phosphate chain can be a monophosphate, diphosphate, or triphosphate. A nucleotide that lacks the phosphate group is called nucleoside.

Nomenclature

Nucleotide names are abbreviated into standard four-letter codes. The first letter is lower case and indicates whether the nucleotide in question is a ribonucleotide (r) or deoxyribonucleotide (d). The second letter indicates the nucleobase:

G: Guanine

A: Adenine

T: Thymine

C: Cytosine

U: Uracil not present in DNA, but takes the place of Thymine in RNA

The third and fourth letters indicate the length of the attached phosphate chain (Mono-, Di-, Tri-) and the presence of a phosphate (P).

For example, deoxy-cytosine-triphosphate is abbreviated as dCTP.

Chemical structures

Nucleotides

Deoxynucleotides

See also

• Gene
• Genetics
• Chromosome

External links

• Abbreviations and Symbols for Nucleic Acids, Polynucleotides and their Constituents (IUPAC)
• Provisional Recommendations 2004 (IUPAC)