WIPO ST.25 is a flat-file format. It is currently the standard way of providing patent offices with sequence listings.
The standard is designed to allow easy modification of sequence listing files using conventional text editors like Notepad. While this is convenient, it makes the files very prone to error.
BiSSAP supports ST.25.
More information
Description: Standard ST.25: Presentation of nucleotide and amino acid sequence listings (May 1998)
Note
ST.25 files are plain-text files. Word documents containing ST.25-file formatting are not compatible with ST.25.