Nucleotide

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 by first indicating whether it is a ribonucleotide (r) or deoxyribonucleotide (d), indicating the nitrogenous base included (G,A,T,C,U), the number of 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 cellularular energy transport and transformations (notably ATP and NAD+/NADH) and in enzyme regulation (see for example, protein kinase).

Nucleotide Codes:

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