On a five-generation pedigree, which feature distinguishes an X-linked-dominant disorder in which males and females are equally affected from an autosomal-recessivepattern of inheritance?
A)The disorder is not apparent until adulthood.
B)Unaffected individuals do not have affected children.
C)There are no instances of an affected father transmitting the disorder to his son.
D)Unaffected parents (who do not express the disorder) do have affected children.

Question

Quizplus · Accepted Answer

With X-linked-dominant transmission of a trait or disorder, an affected father transmits the disorder to all of his daughters (who then express the disorder) and to none of his sons. An affected woman generally has unaffected daughters, affected daughters, unaffected sons, and affected sons in equal proportions. The most notable feature that distinguishes this transmission from that of autosomal recessive is the complete lack of father-to-son transmission because a father cannot transmit an X chromosome to his son (if he did, his son would be his daughter).

On a Five-Generation Pedigree, Which Feature Distinguishes an X-Linked-Dominant Disorder