How should ambiguity symbols be used in nucleotide sequences?

The MPEP 2423.01 provides guidance on using ambiguity symbols in nucleotide sequences:

“For those nucleotides that are ambiguous in designation, the list of one-letter codes given in WIPO Standard ST.25 (1998), Appendix 2, Table 2, must be used.”

Some common ambiguity symbols include:

• n – a or c or g or t/u
• r – a or g (purine)
• y – c or t/u (pyrimidine)
• k – g or t/u
• m – a or c

These symbols allow for the representation of positions where multiple nucleotides are possible. It’s crucial to use these standardized symbols to ensure clarity and consistency in sequence listings.

To learn more:

• ambiguity symbols
• nucleotide sequences
• WIPO Standard ST.25
• sequence listing