Familial vitamin-D-resistant rickets is an X-linked dominant condition in humans. If a man is afflicted with this condition and his wife is normal, it is expected that among their children, all the daughters would be affected and all the sons would be normal. In families where the husband is affected and the wife is normal, this is almost always the outcome among their children when such families have been studied. Very rarely an unexpected result occurs in such families where a boy is born with the disorder. If the chromosomes of such unusual boys are examined, what might be expected to be found?

Question

Quizplus · Accepted Answer

The presence of an extra X chromosome (XXY) could result in a boy inheriting the X-linked dominant condition from his father, as he would have two X chromosomes, one of which could carry the mutation.

Familial Vitamin-D-Resistant Rickets Is an X-Linked Dominant Condition in Humans