Aboy with klinefelter syndrome (47,xxy) is born to a mother who is phenotypically normal and a father who has the x- linked skin condition called anhidrotic ectodermal dysplasia. the mother’s skin is completely normal with no signs of the skin abnormality. in contrast, her son has patches of normal skin and patches of abnormal skin.

a. the father must have contributed the abnormal x-linked gene.
b. the mother must have contributed the abnormal x-linked gene.
c. both parents must have contributed the abnormal x-linked gene.
d. the son’s condition must be the consequence of a spontaneous mutation.

The correct answer is statement a.

Explanation:

The anhidrotic ectodermal dysplasia is featured by unusual skin that loses the tendency to sweat and sparse body hair. It is given that the mother is phenotypically normal, that is, may or may not be a carrier for the condition. Thus, the mother possesses normal skin.  

While the father is affected with ectodermal dysplasia, that is, possesses the mutated X-chromosome. Thus, father has unusual skin. The son is affected by Klinefelter's syndrome and exhibits patches of both abnormal and normal skin.  

Therefore, the son must have inherited the normal X-chromosome from the mother as X-chromosome coming from father is mutated and results in abnormal skin. Hence, it can be concluded that the son inherits the abnormal X-chromosome from the father and the normal X-chromosome from the mother. Thus, the correct answer is option a.