Defining variants: is there a preference for using 'X' versus another possible residue?
X should only be used if there is not a more restrictive symbol that can be used. For instance if the residue is D or N then B should be used in place of X. As indicated in Example 94-1, there is a preferred way of expressing the sequence but more than one way that would be considered acceptable.
Note: there is no need to include a note qualifier if the default value defined in WIPO ST.26 can be assumed