From: Entrez Sequences Quick Start
Entrez Sequences Help [Internet].
Bethesda (MD): National Center for Biotechnology Information (US); 2010-.
NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.
| Nucleotide Codes | |||
| A | adenosine | Y | T or C |
| C | cytidine | M | A or C |
| G | guanine | W | A or T |
| T | thymidine | R | G or A |
| N | A, G, C, or T | B | G, T, or C |
| U | uridine (matches T) | D | G, A, or T |
| K | G or T | H | A, C, or T |
| S | G or C | V | G, C, or A |