Question

Assertion (A): XX – XY type of sex-determination mechanism is an example of male heterogamety.
Reason (R): In birds male heterogamety is observed as males produce two different types of gametes.

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true, but (R) is not the correct explanation of (A).
• C. (A) is true, but (R) is false.
• D. (A) is false, but (R) is true.

Hint:

In humans, males are heterogametic (XY), while in birds, females are heterogametic (ZW).

Answer 1

The Correct Option is C

Step 1: The XX–XY sex-determination system, observed in humans and many other species, demonstrates male heterogamety. This means males generate two distinct gamete types (X and Y), validating Assertion (A).
Step 2: In contrast, avian species exhibit female heterogamety (ZW) and male homogamety (ZZ), rendering Reason (R) inaccurate.
Step 3: As Reason (R) is false, it fails to provide a valid explanation for Assertion (A).
Consequently, (A) is true, while (R) is false.