Hemophilia is caused by several genetic factors; one, a recessive allele of an X- linked gene, is the subject of this problem. Assume that a man with hemophilia marries a normal woman whose father had hemophilia. What is the probability that their first son will have hemophilia?

Question

Quizplus · Accepted Answer

Since hemophilia is a recessive X-linked condition, a man with hemophilia has the genotype X^hY (where X^h represents the hemophilia allele and Y is the normal Y chromosome). A normal woman whose father had hemophilia must be a carrier, as she received one normal X chromosome from her mother and one X^h (hemophilia) chromosome from her father, making her genotype X^hX. When they have a son, the son gets his Y chromosome from his father and has a 50% chance of inheriting the X^h chromosome from his mother, leading to hemophilia.

Hemophilia Is Caused by Several Genetic Factors; One, a Recessive