heterozygous femal

Occasionally a heterozygous female will show some features of the
condition and is referred to as a manifesting carrier. This is usually
due to non-random X inactivation leading to the chromosome
that carries the mutant allele remaining active in most cells. The
process of X inactivation that occurs in early embryogenesis is
normally random, so that most female carriers would have around
50% of the normal gene remaining active, which is sufficient to
prevent clinical signs. Alternatively, X chromosome abnormalities
such as Turner syndrome may give rise to X linked disorders in
females since, like males, they are hemizygous for genes carried by
the X chromosome. The homozygous affected state may occur in
females whose father is affected and whose mother is a carrier.
This is only likely to occur in common X linked disorders such as
red-green colour blindness, or glucose-6-phosphate
dehydrogenase deficiency in the Middle East.