Last updated:2014.11.21.

Nucleotide Base Codes

Codes Used in Sequence Description


The nucleotide base codes that are used with the International Nucleotide Sequence Database is as follows.
Sequence data is expressed with small letters only. Capital letter will be automatically converted to small letter.

Symbol Meaning Explanation
a a adenine
c c cytosine
g g guanine
t t thymine in DNA; uracil in RNA
m a or c amino
r a or g purine
w a or t
s c or g
y c or t pyrimidine
k g or t keto
v a or c or g not t
h a or c or t not g
d a or g or t not c
b c or g or t not a
n a or c or g or t any