Hemophilia is a genetic disorder that causes a protein required for normal blood clotting to be missing. In a cross with a mother who carries the allele for hemophilia and a father who has normal blood clotting what would be the expected phenotypes of the offspring? A. all females normal, all males normal B. all females normal, all males with hemophilia C. all females carriers of hemophilia, all males normal D. one female normal, one male normal, one female carrier, one male with hemophilia

A woman has 2 X chromosomes, so she can carry two copies of the H/h gene. If she carries the dominant allele H in one or two copies she will have normal blood clotting. If the woman has two recessive hh alleles, she will have hemophilia.
A man only has one X chromosome (the other sex chromosme is a Y). If that chromosome has the H allele, he will not have the disease; if he has the h allele, he will be hemophilic.

The cross is between a heterozygous woman with a normal man:

[tex]X^H X^h[/tex] x [tex]X^H Y[/tex]

- The woman produces two types of gametes: [tex]X^H[/tex] and [tex]X^h[/tex]

- The man produces two types of gametes: [tex]X^H[/tex] and [tex]Y[/tex]

As a result of a Punnett Square, the expected offspring will be:

1) [tex]X^H X^H[/tex] : normal female

2) [tex]X^H X^h[/tex] : normal female, carrier of hemophilia

3) [tex]X^H Y[/tex] : normal male

4) [tex]X^h Y[/tex] : hemophilic male

The correct answer is D: one female normal, one male normal, one female carrier, one male with hemophilia