Some genex are located on the X chromosome (X-linked).

Males possess only 1 X chromosome, and exhibit a recessive X-linked trait (such as color blindness) if he inherits the allele from his mother.

A heterozygous female does not exhibit color blindness but is a carrier of the recessive allele.

If a female carrier mates with a normal male:

• There is a 50% chance that a daughter will be a carrier like her mother.

• There is a 50% chance that a son will have the disorder.

Females exhibit the disorder only if she receives the recessive allele from both parents.