Question

Females rarely experience the physiologic defect of haemophilia because they do so only when they are
A. Heterozygous for the defect
B. Homozygous for the defect
C. Carrier for the defect
D. Wives of haemophilic husband

Answer 1

Hint:
Before we proceed into the problem, it is important to know the definition of haemophilia.
Haemophilia is a condition in which there is a lack of functioning blood clotting factors. This often results in excessive bleeding and can be life-threatening. There are two main types of haemophilia, classic and severe disorder (HSC). Classic haemophilia affects about 1 in 5,000 people while HSC affects up to 1% of the population.

Complete step by step solution:
The body is unable to stop the flow of blood in the case of haemophilia and it is a genetically inherited disease.
Even from a minor cut, an infected person will continue to bleed and it is an X-linked disease since the natural phenomenon of blood clotting is not provided by the patient.
The lack of antihemophilic globulin or factor VIII (haemophilia - A) and plasma thromboplastin factor IX is primarily responsible.
Females will develop haemophilia only if homozygous genes on both X chromosomes are available. The condition is referred to as 'carrier' when one dominant and one recessive gene are shared.
Therefore, females rarely experience the physiologic defect of haemophilia because they do so only when they are Homozygous for the defect.

Option ‘B’ is correct

Note:
Because it is an X-linked disease, it affects more men than women. This is due to the fact that females have 2 versions of the X chromosome, and heterozygous females for the gene are disease bearers. A female therefore must have two versions of the faulty gene in order to be hemophilic.