Nucleotide ambiguity code

Code	Represents	Complement
A	Adenosine	T
G	Guanine	C
C	Cytosine	G
T	Thymidine	A
Y	Pyrimidine (C & T)	R
R	Purine (A & G)	Y
W	weak (A & T)	W
S	strong (G & C)	S
K	keto (T & G)	M
M	amino (C & A)	K
D	not C	H
V	not T	B
H	not G	D
B	not A	V
X/N	unknown	X/N

Code example:

Restriction enzyme: AarI
            
Recognition site: CACCTGCNNNN'NNNN_

Cleavage of DNA (/):

 5'- C A C C T G C N N N N/N N N N -3'
 3'- G T G G A C G N N N N N N N N/-5'

The letter codes and compliment translations are those proposed by Nomenclature Committee of the International Union of Biochemistry and Molecular Biology (NC-UIBMB )