Question

Female carriers of X-linked recessive diseases sometimes exhibit some symptoms of the disease. The cause of this is which of the following?

(A) variable expressivity of the X-linked gene
(B) mitochondrial inheritance
(C) skewed X chromosome inactivation
(D) incomplete penetrance of the X-linked gene

Answer 1

Female carriers sometimes show symptoms of X-linked recessive diseases due to skewed X chromosome inactivation, where the normal allele is disproportionately inactivated.

Step-by-step explanation:

The cause of female carriers of X-linked recessive diseases sometimes exhibiting some symptoms of the disease is (C) skewed X chromosome inactivation. X-linked recessive inheritance can result in female carriers who may not show the full phenotype of the disease due to having one normal X chromosome; however, they can still exhibit mild symptoms if the normal X chromosome is randomly inactivated in some cells. This X inactivation process is typically random, but if the inactivation is skewed towards the normal allele, the carrier may express some symptoms of the disease.