AP BIOLOGY

Detailed explanation-1: -There are no genes for clotting factors on the Y chromosome. This means that males only have one allele for factor VIII and one allele for factor IX. Thus, if a male has a hemophilia allele on his only X chromosome, he will have the disorder.

Detailed explanation-2: -Hemophilia is a sex-linked recessive disorder. The abnormal gene responsible for hemophilia is carried on the X chromosome. Males have one X chromosome and one Y chromosome.

Detailed explanation-3: -X-linked recessive inheritance refers to genetic conditions associated with mutations in genes on the X chromosome. A male carrying such a mutation will be affected, because he carries only one X chromosome.

Detailed explanation-4: -Fathers cannot pass X-linked recessive conditions to their sons. When a son inherits a mutated gene on the X chromosome from his mother, the genetic condition is more likely to occur. X-linked recessive conditions most often occur in males.

Detailed explanation-5: -If the mother has one altered factor gene and the father does not have hemophilia, each son has a 50% chance of having hemophilia and each daughter has a 50% chance of having one altered factor gene, causing her to be a carrier or have hemophilia.