A woman homozygous for blood type B marries a haemophilia man. What is the proba

The disease is carried on the X chromosome and is recessive.

The fact that the father has the disease does not affect the sons -- because the father contributes a Y chromosome to them Since the mother is only a carrier, she has one X chromosome that is good and one that is bad. She has a 50% chance of giving the bad one to her sons -- in which case he is a hemophiliac. She also has a 50% chance of having a son who does not carry the gene at all.

Now the daughters get the father's X chromosome (which is bad). and an X chromosome from the mother. If they get the bad one, they will become hemophiliacs. If they get the good one from their mothers, then they will become carriers. There is a zero percent chance that they will be completely clear.

To recap:

Sons: 50% change of hemophelia -- 50% chance of being clear of it

Daughters: 50% chance of hemophilia -- 50% chance of being a carrier.

Hemophilia is a sex linked recessive trait, so the it is only on the x chromosome. A woman who is a carrier is Xh X. The man is Xh Y. If they have a boy, he will either be Xh Y or X Y, so 1/2 chance of being hemophiliac. A girl will be either Xh Xh or Xh X. So she has a 1/2 chance too. So any child has one half probability of being hemophiliac.

Notice that sex linked ressecive means that :
Xh X is a female carrier, the X with nothing can be written as XH, meaning that is has a dominant H that masks the Xh. Thus the girl is only "carrying" the trait and not expressing it.

XhXh means that you have to ressecive traits, so you will definitely express it.

Y chromosomes don't have the "h" trait. So in males, if there is an Xh, the male will definitely express it. There would be nothing to mask the Xh because the Y cannot be "YH" (no such things).

The only way a male can be normal is if he does not get any defective Xh from mom.

25% of females may be haemophilic
25% of females may be carriers
25% of males may be haemophilic
25% of males may be healthy

I believe there is a 75% chance their offspring will have Haemophilia. They can only give birth to a Haemophiliac female carrier, as female offspring suffering from the disease will terminate, which leaves male carriers and sufferers.....