question_answer

A woman has an X-linked condition on one of her X-chromosomes. This chromosome can be inherited by

A) Only grand children

B) Only sons

C) Only daughters

D) Both [b] and [c]

Correct Answer: D

Solution :

[d] In the given problem, the woman has an X-linked condition and she can transmit the carrier allele to both her son and daughter. The resulting son will be affected because X-linked disorder always affect males as males contain a single X-chromosome. The daughter offspring will be a carrier, but not diseased because females are affected by X-linked disorder in homozygous recessive condition only, i.e. two recessive alleles are required. Hence, out of the 4 offspring possible 25% of sons are diseased and 25% are normal. Similarly, 50% daughters normal out of which half are carriers.