Hemophilia is a trait carried by the mother and passed to her sons. The allele for hemophilia, therefore,
A) is carried on one of the mother's autosomal chromosomes.
B) is carried on the Y chromosome.
C) can be carried on the X or Y chromosome.
D) is on the X chromosome and can only be inherited by the son if the mother is a carrier (heterozygous).
E) is carried in the mitochondrial genome because sons inherit this allele from their mothers.

Question

Quizplus · Accepted Answer

Hemophilia is caused by a recessive allele located on the X chromosome. As males only inherit one X chromosome from their mother, they will have the disorder if they inherit the affected X chromosome. Females need to inherit two copies of the allele to have hemophilia, as they have two X chromosomes. Therefore, hemophilia is carried on the X chromosome and can only be inherited by the son if the mother is a carrier (heterozygous).

Hemophilia Is a Trait Carried by the Mother and Passed