Question

Assertion (A): The Y Chromosome has no role in the determination of male sex in Drosophila.
Reason (R): In XO males, sperms develop but are non-motile.

• A. A and R are true. R is correct explanation for A.
• B. A and R are true. But R is not correct explanation for A.
• C. A is true. But R is false.
• D. A is false. But R is true.

Hint:

In Drosophila, male sex determination is not based on the presence of the Y chromosome. The sex determination is determined by the ratio of X chromosomes to autosomes.

Answer 1

The Correct Option is B

- Assertion (A): The Y chromosome is not directly responsible for determining male sex in Drosophila. Male sex determination is based on the ratio of X chromosomes to autosomes. In XO males, the absence of a second X chromosome is responsible for male development. True.

- Reason (R): In XO males, the sperm cells do develop, but they are non-motile due to a lack of functional cilia or flagella. This is a true statement. True.

- Explanation: Although both the assertion and reason are true, the reason does not directly explain the assertion. The Y chromosome does not play a significant role in the determination of male sex in Drosophila, and the non-motility of sperm in XO males is not directly related to this fact.

Thus, the correct answer is Option B, which is: A and R are true. But R is not the correct explanation for A.