Assertion: The Y-chromosome is called androsome.
Reason: X and Y-chromosomes differ in form and size.

Options

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

Answer

**Step-by-Step Solution:**

1. **Understanding the Assertion:**
- The assertion states that the Y-chromosome is called androsome. This term is derived from the Greek word "andro," meaning male, indicating that the Y-chromosome is associated with male sex determination in humans.

2. **Understanding the Reason:**
- The reason provided states that X and Y chromosomes differ in form and size. This is true; the X chromosome is larger and has more genes compared to the smaller Y chromosome. This difference in size and shape makes them heteromorphic chromosomes.

3. **Analyzing the Relationship:**
- While both the assertion and reason are true, the reason does not directly explain why the Y-chromosome is called androsome. The term "androsome" specifically refers to its role in male sex determination, not merely its size or form.

4. **Evaluating the Options:**
- Based on the analysis:
- Option 1 states both are true and the reason explains the assertion (incorrect).
- Option 2 states both are true but the reason does not explain the assertion (correct).
- Option 3 states assertion is true but reason is false (incorrect).
- Option 4 states both are false (incorrect).

5. **Conclusion:**
- The correct answer is that both the assertion and reason are true, but the reason is not the correct explanation of the assertion.