Question

Hemophilia is a sex-linked disorder. Males who receive the allele are always affected. Females are affected only 25% of the time. Which kind of inheritance must hemophilia display and why?(1 point)
Responses

Y-linked recessive because the males that receive the allele sometimes have hemophilia.
Y-linked recessive because the males that receive the allele sometimes have hemophilia.
Y-linked dominant because all males with the allele have hemophilia.
Y-linked dominant because all males with the allele have hemophilia.
X-linked recessive because all males with the allele have hemophilia, and only some females if they receive two recessive alleles.
X-linked recessive because all males with the allele have hemophilia, and only some females if they receive two recessive alleles.
X-linked dominant because everyone with the allele has hemophilia.

Answer 1

The correct response is:

**X-linked recessive because all males with the allele have hemophilia, and only some females if they receive two recessive alleles.**

**Explanation:** Hemophilia is typically caused by a mutation on the X chromosome. Males (XY) have only one X chromosome; thus, if they inherit the mutated allele, they will display symptoms of hemophilia. Females (XX) have two X chromosomes, so they must inherit two copies of the recessive allele (one from each parent) to be affected; hence, they are affected only 25% of the time if one of their X chromosomes carries the recessive allele.