is sex-linked. X-linked dominant inheritance Each child of a mother affected with an X-linked dominant trait has a 50% chance of inheriting the mutation and thus being affected with the disorder. If only the father is affected, 100% of the daughters will be affected, since they inherit their father's X chromosome, and 0% of the sons will be affected, since they inherit their father's Y chromosome. There are fewer X-linked dominant conditions than X-linked recessive, because dominance in X-linkage requires the condition to present in females with only a fraction of the reduction in gene expression of autosomal dominance, since roughly half (or as many as 90% in some cases) of a particular parent's X chromosomes are inactivated in females. Examples Alport syndrome Coffin–Lowry syndrome (CLS) Fragile X syndrome Idiopathic hypoparathyroidism Incontinentia pigmenti Rett syndrome (RS) Vitamin D resistant rickets (X-linked hypophosphatemia) X-linked recessive inheritance Females possessing one X-linked recessive mutation are considered carriers and will generally not manifest clinical symptoms of the disorder, although differences in X chromosome inactivation can lead to varying degrees of clinical expression in carrier females since some cells will express one X allele and some will express the other. All males possessing an X-linked recessive mutation will be affected, since males have only a single X chromosome and therefore have only one copy of X-linked genes. All offspring of a carrier female have a 50% chance of inheriting the mutation if the father does not carry the recessive allele. All female children of an affected father will be carriers (assuming the mother is not affected or a carrier), as daughters possess their father's X chromosome. If the mother is not a carrier, no male children of an affected father will be affected, as males only inherit their father's Y chromosome. The incidence of X-linked recessive conditions in females is the square of that in males: for example, if 1 in 20 males in a human population are red–green color blind, then 1 in 400 females in the population are expected to be color-blind (1/20)*(1/20). Examples Aarskog–Scott syndrome Adrenoleukodystrophy (ALD) Bruton's agammaglobulinemia Color blindness Complete androgen insensitivity syndrome Congenital aqueductal stenosis (hydrocephalus) Duchenne muscular dystrophy Fabry disease Glucose-6-phosphate dehydrogenase deficiency Haemophilia A and B Hunter syndrome Inherited nephrogenic diabetes insipidus Menkes disease (kinky hair syndrome) Ornithine carbamoyltransferase deficiency Wiskott–Aldrich syndrome Y-linked Various failures in the SRY genes Sex-linked traits in other animals White eyes in