How are nucleotide bases represented in a sequence listing?

This page is an FAQ based on guidance from the Manual of Patent Examining Procedure. It is provided as guidance, with links to the ground truth sources. This is information only: it is not legal advice.

Nucleotide bases in a sequence listing are represented using specific symbols as outlined in WIPO Standard ST.25 and referenced in MPEP 2423.01. The representation follows these guidelines:

• Use the one-letter code for nucleotide sequence bases: A, C, G, T for DNA; A, C, G, U for RNA
• The letters must be capital letters
• For modified bases, use “n” in the sequence and provide details in the Feature section
• Use “n” for unknown bases

The MPEP states:

“The bases in a nucleotide sequence must be represented using the one-letter code for nucleotide sequence characters as presented in WIPO Standard ST.25 (1998), Appendix 2, Table 1.”

Adhering to these standardized representations ensures clarity and consistency in nucleotide sequence listings across patent applications.