37 CFR Part 1, Appendix A
Verified against eCFR.gov as of June 20, 2026View official text on eCFR.gov ↗
Source: World Intellectual Property Organization (WIPO) Handbook on Industrial Property Information and Documentation, Standard ST.25: Standard for the Presentation of Nucleotide and Amino Acid Sequence Listings in Patent Applications (2009).
| Symbol | Meaning | Origin of designation |
|---|---|---|
| a | a | adenine. |
| g | g | guanine. |
| c | c | cytosine. |
| t | t | thymine. |
| u | u | uracil. |
| r | g or a | purine. |
| y | t/u or c | pyrimidine. |
| m | a or c | amino. |
| k | g or t/u | keto. |
| s | g or c | strong interactions 3H-bonds. |
| w | a or t/u | weak interactions 2H-bonds. |
| b | g or c or t/u | not a. |
| d | a or g or t/u | not c. |
| h | a or c or t/u | not g. |
| v | a or g or c | not t, not u. |
| n | a or g or c or t/u, unknown, or other | any. |
[86 FR 57052, Oct. 14, 2021]