标准核酸（DNA、RNA）代码（符号）表
Standard IUB/IUPAC nucleic acid codes (symbols) table
Code Nucleic Acid(s)
A---- Adenine
C---- Cytosine
G---- Guanine
T---- Thymine
U---- Uracil
M---- A or C (amino)
R---- A or G (purine)
W---- A or T (weak)
S---- C or G (strong)
Y---- C or T (pyrimidine)
K---- G or T (keto)
V---- A or C or G
H---- A or C or T
D---- A or G or T
B---- C or G or T
N---- A or G or C or T (any)
