Haemophilia is more commonly seen in human males than in human females because

Options

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

Explanation

**Step-by-Step Solution:**

1. **Understanding Hemophilia**: Hemophilia is a genetic disorder that affects the blood's ability to clot, leading to excessive bleeding. It is primarily caused by mutations in genes located on the X chromosome.

2. **X-Linked Inheritance**: Hemophilia is classified as an X-linked recessive disorder. This means the gene responsible for hemophilia is located on the X chromosome, and the disorder manifests in individuals who have a specific genetic makeup.

3. **Genetic Makeup of Males and Females**:
- Males have one X chromosome and one Y chromosome (XY).
- Females have two X chromosomes (XX).

4. **Impact of X-Linked Recessive Mutations**:
- In males, having just one affected X chromosome (X^hY) is enough for hemophilia to manifest because there is no second X chromosome to potentially mask the effect of the mutated gene.
- In females, both X chromosomes must carry the mutation (X^hX^h) for hemophilia to manifest. If they have one normal X chromosome (X^hX), they will not show symptoms but can be carriers.

5. **Conclusion**: Since males only need one copy of the mutated gene to express hemophilia, while females need two, hemophilia is more commonly seen in males than in females.

6. **Final Answer**: Hemophilia is more commonly seen in human males than in human females because it is due to an X-linked recessive mutation.

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