DNA base ambiguity codes
Last modified on July 24, 2026 • 1 min read • 74 wordsSometimes you don’t know what nucleotide base you are dealing with or you need to specific a degenerate oligo.
| Code | Meaning | Bases |
|---|---|---|
| A | Adenine | A |
| C | Cytosine | C |
| G | Guanine | G |
| T | Thymine | T |
| R | puRine | A, G |
| Y | pYrimidine | C, T |
| S | Strong (3 H-bonds) | G, C |
| W | Weak (2 H-bonds) | A, T |
| K | Keto | G, T |
| M | aMino | A, C |
| B | not A | C, G, T |
| D | not C | A, G, T |
| H | not G | A, C, T |
| V | not T | A, C, G |
| N | Any base | A, C, G, T |