A woman's father has hemophilia (an x-linked recessive trait which results in abnormally long blood clotting times), but she has normal blood clotting, so does her husband. What genotypes are possible among her offsprings and what proportion of her sons would be hemophiliac?
The woman's father has hemophilia therefore she is a carrier. Being a carrier, she possesses a genotype of XX`^r` where X`^r` is the recessive trait for hemophilia. Since her husband has a normal blood clotting, he is unaffected and thus have a genotype of XY. To know the possible genotypes of the offspring, we shall employ the usage of punnett square.
X XX XY
X`^r` XX`^r` X`^r`Y
The possible genotypes of the offspring are:
25% XX or unaffected (normal) female
25% XY or unaffected (normal) male
25% XX`^r` or carrier female
25% X`^r`Y or Affected (hemophiliac) male