Question

Recently a girl baby has been reported to suffer from haemophilia. How is it possible? Explain with the help of a cross.

Answer 1

Haemophilia is an X- linked recessive inheritance disease and it is non-communicable disease and hence can only be transferred to offsprings genetically. Haemophilia is a disease in which the individual lacks blood clotting factor -VIII and hence blood clotting is not possible.

Haemophilia is caused when there is heamophilic gene in all the X chromosomes of an individual. So for a male to have heamophilia , he should have the haemophilic gene in the only X chromosome he has. In females, haemophilia is expressed if there is haemophilic gene in both the X chromosomes and a female with haemophilic gene in only one X chromosome is called carrier of haemophilia.

Therefore for the girl baby to have haemophilia, there two cases possible

1. If both mother and father have haemophilia.

2. if the mother is carrier and father has haemophilia.

The inheritance is explained in the given image below.