Haemophiliais 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

Answer

**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 also known as "Bleeder's disease."

2. **Genetic Basis of Hemophilia**: Hemophilia is caused by a mutation in a gene that is located on the X chromosome. This gene is responsible for producing a protein essential for blood clotting.

3. **Inheritance Pattern**: Hemophilia is inherited in an X-linked recessive manner. This means that the gene for hemophilia is recessive and located on the X chromosome.

4. **Sex Differences in Chromosomes**: Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). Because males have only one X chromosome, if they inherit the hemophilia gene on that X chromosome, they will express the disease.

5. **Females as Carriers**: For a female to express hemophilia, she must inherit the defective gene from both parents, making her homozygous recessive (XhXh). If she has only one defective gene (XhX), she will be a carrier but not express the disease.

6. **Conclusion**: Since males only need one copy of the recessive gene to express hemophilia, they are more commonly affected than females, who require two copies of the recessive gene.

7. **Correct Answer**: The correct answer to the question is that hemophilia is more commonly seen in human males than in human females because the disease is due to an X-linked recessive mutation.