Assertion (A) : Haemophilia is a recessive sex linked disease.
Reason (R ) : Haemophilia occurs due to mutation of a structural gene on chromosome 15.

Options

A. If both assertion and reason are true reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false.

Explanation

To analyze the given question, we will evaluate both the assertion and the reason provided.

### Step 1: Understanding the Assertion
- **Assertion (A)**: "Haemophilia is a recessive sex-linked disease."
- Haemophilia is indeed a recessive disorder that is linked to the X chromosome. This means that males (who have only one X chromosome) are more likely to express the disease, while females (who have two X chromosomes) can be carriers without showing symptoms.

### Step 2: Understanding the Reason
- **Reason (R)**: "Haemophilia occurs due to mutation of a structural gene on chromosome 15."
- This statement is incorrect. Haemophilia is caused by mutations in genes located on the X chromosome, specifically the genes responsible for producing clotting factors VIII and IX. Chromosome 15 is not involved in the genetic basis of haemophilia.

### Step 3: Evaluating the Relationship
- Since the assertion is true and the reason is false, we can conclude that the correct relationship between the two statements is that the assertion is true, but the reason is false.

### Final Conclusion
- The correct answer is: Assertion is true, but reason is false.

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