A
mode of inheritance in which a mutation in a gene on the X chromosome causes
the phenotype to be expressed in males who are hemizygous for the gene mutation
(i.e., they have only one X chromosome) and in females who are homozygous
for the gene mutation (i.e., they have a copy of the gene mutation on each
of their two X chromosomes). Carrier females who have only one copy of the
mutation do not usually express the phenotype, although differences in X-chromosome
inactivation can lead to varying degrees of clinical expression in carrier
females
Definition from: GeneTests
from the University of Washington and the National Center for Biotechnology Information