IUPAC codes
| The International Union of Pure and Applied Chemistry (IUPAC) has defined a standard representation of DNA bases by single characters that specify either a single base (e.g. G for guanine, A for adenine) or a set of bases (e.g. R for either G or A). UCSC uses these single character codes to represent multiple observed alleles of single-base polymorphisms.
Symbol | Bases | Origin of designation
--- | --- | ---
G | G | Guanine
A | A | Adenine
T | T | Thymine
C | C | Cytosine
R | G or A | puRine
Y | T or C | pYrimidine
M | A or C | aMino
K | G or T | Keto
S | G or C | Strong interaction (3 H bonds)
W | A or T | Weak interaction (2 H bonds)
H | A or C or T | not-G, H follows G in the alphabet
B | G or T or C | not-A, B follows A
V | G or C or A | not-T (not-U), V follows U
D | G or A or T | not-C, D follows C
N | G or A or T or C | aNy