Question

Haemophilia is more commonly seen in human males than in human females because
A. This disease is due to an X-linked dominant mutation.
B. A greater proportion of girls die in infancy.
C. This disease is due to an X-linked recessive mutation.
D. This disease is due to a Y-linked recessive mutation.

Answer 1

Hint:
Before we proceed into the problem, it is important to know the definition of Hemophilia.
Haemophilia is a genetic blood clotting disorder in which the blood fails to clot normally. This can result in both impulsive and post-injury or surgical bleeding. Blood includes several proteins known as clotting factors that can aid in the prevention of bleeding.

Complete step by step solution:
Haemophilia is an X-linked recessive condition. Because it is a recessive disorder, it manifests only in homozygous recessive circumstances. Human males have one copy of the X-chromosome; hence one copy of the damaged gene in each cell is enough to produce the condition (X^cX). As a result of being an X-linked recessive mutation, it is more common in males.
Females have two X-chromosomes, and females who have two copies of the affected gene have the condition (X^cX^c). Females who are heterozygous (X^cX) for this characteristic are normal but function as disease carriers. If it was a Y-linked illness, it would have been more prevalent in men because men have one copy of the Y-chromosome and can express both recessive and dominant Y-linked genes.
Therefore, Haemophilia is more commonly seen in human males than in human females because this disease is due to an X-linked recessive mutation.

Option ‘C’ is correct

Note:
X-linked recessive inheritance refers to genetic abnormalities caused by mutations in X-chromosome genes. A male with such a mutation will be affected because he only has one X chromosome. A female with a mutation in one gene and a normal gene on the other X chromosome is unaffected.