Write short note Haemophilia .
Sickle cell anaemia is
Red green colour blindness appears due to
Assertion : Haemophilia is a recessive sex linked disease.
Reason : Haemophilia occurs due to mutation of a structural gene on chromosome $15$.
The most striking example of point mutation is found in a disease called
A woman has a haemophilic son and three normal children. Her genotype and that of her husband with respect to this gene would be