If the sequences are in a list, they must all be of the same length.
If strict = FALSE
(the default), the following rule is used to
determine if a site is polymorphic or not in the presence of ambiguous
bases: `A' and `R' are not interpreted as different, `A' and `Y' are
interpreted as different, and `N' and any other base (ambiguous or
not) are interpreted as not different. If strict = TRUE
, all
letters are considered different.
Alignment gaps are considered different from all letters except for
the leading and trailing gaps if trailingGapsAsN = TRUE
(which
is the default).