Question: 177: A normal girl, whose mother is haemophilic marries a male with no ancestral history of haemophilia. What will be the possible phenotypes of the offsprings?
(a) Haemophilic son and haemophilic daughter.
(b) Haemophilic son and carrier daughter.
(c) Normal daughter and normal son.
(d) Normal son and haemophilic daughter.
Choose the most appropriate answer from the options given below :
(1) (a) and (b) only
(2) (b) and (c) only
(3) (a) and (d) only
(4) (b) and (d) only
Answer: Option (2)
Explanation:
Haemophilia is an X-linked recessive disorder.
A haemophilic mother has the genotype X^{h}X^{h}.
Therefore, a normal girl born to her must be a carrier with genotype X^{H}X^{h}.
The male with no ancestral history of haemophilia is normal and has the genotype X^{H}Y.
On crossing X^{H}X^{h} with X^{H}Y, the possible offspring are:
Daughters: X^{H}X^{H} (normal daughter) and X^{H}X^{h} (carrier daughter).
Sons: X^{H}Y (normal son) and X^{h}Y (haemophilic son).
Thus, the possible phenotypes include haemophilic son with carrier daughter and normal son with normal daughter.
Therefore, the correct statements are (b) and (c), corresponding to option (2).