Question

A man whose father was a hemophiliac, but whose own blood clotting time is normal, marries a normal woman with no record of hemophilia in her ancestry. what is the chance of hemophilia in their children

Answer 1

The children of a man with a hemophiliac father and a normal woman have no chance of inheriting hemophilia if the mother is not a carrier and the father's blood clotting is normal.

Step-by-step explanation:

The chance of hemophilia in the children of a man with a hemophiliac father and a normal woman is dependent on the carrier status of the woman. Since the woman has no record of hemophilia in her ancestry, it is likely she is not a carrier of the defective gene. Hemophilia is a sex-linked trait, commonly associated with the X chromosome. A man will pass on his Y chromosome to his sons, so they cannot inherit hemophilia from him; they would inherit only the normal X chromosome from their mother.

Daughters, however, will inherit the father's X chromosome. If the father has a recessive allele for hemophilia on his X chromosome (which he does not, as his clotting is normal), there would be a risk for the daughters to become carriers. But since the father's clotting is normal, this indicates he does not have the hemophilia allele on his X chromosome. Therefore, any daughters or sons they have would not inherit hemophilia from their parents under these circumstances.

Answer 2

The correct answer would be zero percent.

Hemophilia is an X linked recessive disorder, thus, in females, two copies of the mutated gene are required to cause the disease while in males only one copy of the mutated gene is enough to produce the phenotype as males contain only one X chromosome.

As the man is normal or non-hemophiliac, his genotype would be
`X^(C)Y`.

Similarly, the female is also normal with no ancestry of hemophilia. Thus, the genotype of this female would be
`X^(C)X^(C)`.

The cross would result in the production of children, all having normal genotype.

Thus, the chances of hemophilia in their children are zero.