Question

Assertion (A): Human female has a perfect pair of sex chromosomes.
Reason (R): Sex chromosome contributed by the human male in the zygote decides the sex of a child.

• 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.

Answer 1

The Correct Option is B

Step 1: Understanding the assertion (A):
Assertion (A) states that a human female has a perfect pair of sex chromosomes. This is a factual statement as the sex chromosomes in a female are two X chromosomes (XX), which are identical in structure. Therefore, this assertion is true. The two X chromosomes in females are considered a "perfect pair" as they are homologous, meaning they contain similar genetic material related to female characteristics.

Step 2: Understanding the reason (R):
Reason (R) suggests that the sex chromosome contributed by the human male in the zygote decides the sex of the child. This is also a true statement. The sex of a child is determined by the male’s contribution, as the female can only provide an X chromosome (due to her XX sex chromosomes). The male, on the other hand, can contribute either an X or a Y chromosome. If the male contributes an X chromosome (XX), the child will be female. If the male contributes a Y chromosome (XY), the child will be male. Therefore, the male's sex chromosome is the determining factor in the child’s sex.

Step 3: Analyzing the relationship between assertion and reason:
While both the assertion and the reason are individually correct, Reason (R) does not directly explain Assertion (A). The fact that a female has a perfect pair of sex chromosomes (XX) is inherent to her biology and is not determined by the male’s contribution. The male's contribution, which determines the sex of the child, is unrelated to the concept of a "perfect pair" of sex chromosomes in females. Hence, Reason (R) does not serve as the correct explanation for Assertion (A).

Step 4: Conclusion:
The correct response is: Both (A) and (R) are true, but (R) is not the correct explanation of (A). Although both statements are factual, Reason (R) explains sex determination but does not explain the concept of a "perfect pair" of sex chromosomes in a female.