Nucleotide
| Code | Equivalence | Complement |
|---|---|---|
| A | A | T |
| C | C | G |
| G | G | C |
| T or U | T | A |
| M | A or C | K |
| R | A or G | Y |
| W | A or T | W |
| S | C or G | S |
| Y | C or T | R |
| K | G or T | M |
| V | A or C or G | B |
| H | A or C or T | D |
| D | A or G or T | H |
| B | C or G or T | V |
| X or N | A or C or G or T | X |
A nucleotide is an organic molecule consisting of a nitrogenous heterocyclic base (a purine or a pyrimidine), a pentose sugar (deoxyribose in DNA or ribose in RNA), and a phosphate or polyphosphate group. (A nucleoside is similar, except that it contains only the sugar and base, without a phosphate.)
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 nitrogenous base included (G,A,T,C,U). The third and fourth letters indicate the number of attached phosphates (Mono-, Di-, Tri-) and the presence of a phosphate (P). For example, deoxy-cytosine-triphosphate is abbreviated as dCTP.
Nucleotides are the monomers of nucleic acids and also play important roles in cellular energy transport and transformations (notably ATP and NAD+/NADH) and in enzyme regulation (see for example, protein kinase).
See also
de:Nukleotid es:Nucleótido fr:Nucléotide nl:Nucleotide ja:ヌクレオチド pl:Nukleotyd pt:Nucleótido sv:Nukleotid