Glossary — X-linked recessive trait

X-linked recessive trait

A trait transmitted by a gene located on the X chromosome; also called a sex-linked trait. Because males have only one X chromosome, a single recessive mutation on that X is sufficient to cause the disorder. Females have two X chromosomes and are typically carriers if only one copy of the gene is mutated.

X-linked recessive inheritance when father is affected and mother is unaffected If the father is affected and the mother is unaffected:
  • All daughters will be carriers.
  • All sons will be unaffected.
X-linked recessive inheritance when mother is a carrier and father is unaffected If the father is unaffected and the mother is a carrier:
  • One daughter out of two will be a carrier.
  • One son out of two will be affected.
X-linked recessive inheritance when mother is affected and father is unaffected If the father is unaffected and the mother is affected:
  • All daughters will be carriers.
  • All sons will be affected.
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