Question

What is probability of the offspring daughter will be haeimophilic if a haemophilic man marries a normal homozygous woman?

Options

• 0%

• 50%

• 75%

• 100%

Answer 1

0%

Explanation:

Haemophilia is a sex-linked recessive disorder carried on the X chromosome. A haemophilic man has the genotype X^h Y (where X^h is the affected X chromosome). A normal homozygous woman has the genotype X^H X^H (both normal X chromosomes). The daughters get one X chromosome from the father (which is affected, X^h) and one X chromosome from the mother (which is normal, X^H). Hence, all daughters will be carriers (X^H X^h) but phenotypically normal (not haemophilic). Therefore, the probability that a daughter will be haemophilic (having both X chromosomes affected, which is not possible here) is zero.