Question

If a father shows a normal genotype and mother shows a carrier trait for haemophilia, then
A. All the female children will be a carrier
B. A Male child has $50\%$ chances of active disease
C. Female child has a probability of $50\%$ of active disease
D. All of the female children will be colour blind

Answer 1

Haemophilia is a congenital abnormality characterized by bleeding from an injured part due to non-clotting of blood. The treatment can be done to clot blood but this condition cannot be cured.

Complete answer:
The haemophilia is a sex-linked recessive disease which shows its transmission from an unaffected female carrier to some of the male progeny. In this disease, a single protein that is a part of the cascade of proteins involved in the coagulation of blood is affected. As a result of this, in an infected individual, a simple cut will result in non-stop bleeding. The heterozygous female carrier for haemophilia may transfer the disease to sons. The probability of the female becoming haemophilic is very rare because the mother of such a female has to be at least a carrier while the father should be haemophilic.
It is an inherited genetic disorder which results in the deterioration of the formation of a blood clot. In a condition, where the father is normal and the mother is the carrier of haemophilia disease, then the female offspring that are produced may be normal or the carrier of the disease. But there is a chance that the male offspring will have $50\%$ chances of the active state.
Hence, the correct answer is, ‘B. A Male child has $50\%$ chances of active disease’.

Note: The haemophilia is found more in males than in females because only one haemophilia gene is required to affect a male with this disease but to be a female haemophilic two haemophilia genes are necessary. The first haemophilia was found in the Queen Victoria of England.