A.1 Nucleotide Codes

We have included a list of accepted nucleotide replacement combinations and their respective symbols. The symbols are commonly found in output data from sequencing instruments. Table A-1 shows the complete set of nucleotide codes.

Table A-1. Nucleotide codes

Symbol	Acceptable nucleotides	Name or type	Complement
G	G	Guanine	C
A	A	Adenine	T
T	T	Thymine	A
C	C	Cytosine	G
R	G or A	purine	Y
Y	T or C	pyrimidine	R
M	A or C	amino	K
K	G or T	keto	M
S	G or C		S
W	A or T		W
H	A or C or T		D
B	G or T or C		V
V	G or C or A		B
D	G or A or T		H
N	G or A or T or C	any nucleotide	N