Sex-linked conditions are more common in men than in women because
A)men acquire two copies of the defective gene during fertilization.
B)men need to inherit only one copy of the recessive allele for the condition to be fully expressed.
C)the sex chromosomes are more active in men than in women.
D)the genes associated with the sex-linked conditions are linked to the Y chromosome, which determines maleness.

Question

Quizplus · Accepted Answer

Sex-linked conditions are caused by genes located on the sex chromosomes. Men have one X and one Y chromosome, while women have two X chromosomes. If a man inherits a recessive allele for a sex-linked condition on his X chromosome, he will express the condition because he does not have a second X chromosome with a healthy copy of the gene to mask the effects of the mutant gene. In contrast, women need to inherit two copies of the recessive allele for the condition to be fully expressed because they have two X chromosomes. Therefore, sex-linked conditions are more common in men than in women because men need only one copy of the recessive allele to show the effect, which occurs on their single X chromosome.

Sex-Linked Conditions Are More Common in Men Than in Women