Nucleotide Base Codes
Codes Used in Sequence Description
Nucleotide
- Nucleotide Base Codes
- Modified Base Abbreviations
Amino Acid
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 |
- References
- Cornish-Bowden, A. Nucl Acid Res 13, 3021-3030 (1985)
- DDBJ/EMBL/GenBank Feature Table Definition 7.4.1 Nucleotide base codes (IUPAC)