Doctor Kryskowski: In this family a young man is affected with an X-linked recessive disorder. In these disorders we often see more affected men
than women, as a man with a mutation on his X chromosome will be
affected, whereas a woman heterozygous for the mutation will be an
unaffected carrier. In this case the mother of the young man must be a
heterozygous carrier of the disease, as he has inherited his X
chromosome with the mutation from her. What is the risk that the man's
sibling (indicated 2) and child (indicated 1) will develop the disease,
provided that the man's wife is not a carrier?
IIOOL
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