Questions & Answers

Haemophilic carrier female marries a normal man. In the progeny
A) All daughters will have haemophilia
B) All sons will have haemophilia
C) 50% daughters will have haemophilia
D) 50% sons will have haemophilia

Answer Verified Verified
Hint: Haemophilia is a genetic disorder. In this disease, the body loses the ability to form blood clots needed to stop bleeding. This disease is inheritable.

Complete Answer:
- Haemophilia is a genetic disorder. It is an X- linked chromosome disease in which X carries a non-functional gene. It is of two types haemophilia A which occurs due to low amount of clotting factor VIII, haemophilia B which occurs due to low level of clotting factor IX.
- The haemophilia is an X-linked recessive gene. It means females are the carrier of haemophilia. It will be only expressed if the female combination is double recessive.
- If a haemophilic carrier mother which means haemophilia is expressed in the recessive gene expressed as Xx where x represents the recessive haemophilia X linked gene is crossed with the normal man whose gene is represented as XY. The offsprings would be as follows-
The offspring produced are 50% females in which out of 2 one daughter is the carrier and one is normal. And in case of sons, one is normal and the other is diseased.

Thus the correct answer is (D) 50% sons will have haemophilia.

Note: Haemophilia is X recessive linked gene disorder. A carrier mother has 50% chance of transferring the disease to her daughter. An affected male will pass on the genes to the daughters.