The USPTO's preferred method for submitting a "Sequence Listing" is as an ASCII plain text file via the USPTO patent electronic filing system. The MPEP states: Filing the "Sequence Listing" as an ASCII plain text file submitted via the USPTO patent electronic filing system that complies with both 37 CFR 1.821(c) and (e) is the Office's preferred method of receiving a "Sequence Listing". This method is preferred because: It serves as both the "Sequence Listing" required by 37 CFR 1.821(c) and the CRF required by 37 CFR 1.821(e) It eliminates any chance for discrepancies between two separate submissions The ASCII plain text file is not included in the application size fee determination under 37 CFR 1.52(f)(1) or (2) By submitting the "Sequence Listing" in this format, applicants can streamline their submission process and reduce potential errors. To learn more: sequence listing ASCII plain text USPTO patent application electronic filing