Traits controlled by sex-linked recessive genes are expressed more often in males because
A) males always carry two copies of these genes.
B) all male offspring of a female carrier get the gene.
C) males inherit these genes from their fathers more often than their mothers.
D) the male has only one gene for the trait.
E) males get more doses of the recessive gene than do females.

Question

Quizplus · Accepted Answer

Males have only one X chromosome (and one Y chromosome), so they have only one copy of genes that are located on the X chromosome. If a male inherits a recessive gene on the X chromosome, he will express the trait because there is no corresponding gene on the Y chromosome to mask the recessive gene. This is why sex-linked recessive traits are expressed more often in males.

Traits Controlled by Sex-Linked Recessive Genes Are Expressed More Often