Question

A woman with normal blood clotting ability whose father was a hemophiliac and whose mother was normal with no family history of hemophilia marries a man whose blood has normal clotting ability. Recall that hemophilia is an X-linked trait. What is the probability that their first child will be a son with hemophilia

Answer 1

The answer is 25%.

Step-by-step explanation:

Hemophilia is a recessive illness that is x-linked.

If the husband has normal clotting ability, that means he has the dominant gene since he has only one X chromosome.

Since there is a probability that their child will have hemophilia, this means that the woman, who has 2 X chromosomes but has normal blood clotting abilities, has one dominant and one recessive hemophilia gene.

The probability that their first child will be a male is 50% and the probability that he will have hemophilia is also 50% since he will only get the Y chromosome from the father and the mother has one dominant and one recessive.

So the probability that their first child will be a son with hemophilia is 25%.

I hope this answer helps.