Question

two statements are given — one labelled as Assertion (A) and the other labelled as Reason (R). Select the correct answer to these questions from the codes (A), (B), (C) and (D) as given below.
Assertion (A): Chromosomes inherited from the parents decide the sex of a child.
Reason (R): Y chromosome in a male child is inherited from the father.

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

Answer 1

The Correct Option is B

Step 1: Understanding the Assertion (A):
The assertion states that a child's sex is determined by the sex chromosomes inherited from both parents. The mother invariably contributes an X chromosome. The father can contribute either an X or a Y chromosome. An XX combination results in a female, while an XY combination (X from mother, Y from father) results in a male.

Step 2: Understanding the Reason (R):
The reason explains that a male child inherits a Y chromosome from the father, with the mother always contributing an X. The Y chromosome is the primary determinant of male sex due to genes like SRY, which initiate the development of male reproductive structures.

Step 3: Connecting Assertion (A) and Reason (R):
- The assertion addresses the inheritance of sex chromosomes and their role in sex determination.
- The reason elaborates on the mechanism: the father's Y chromosome leads to a male child, while the mother only provides an X.
- The reason directly supports and explains the assertion, as it details the genetic basis for the Y chromosome determining male sex.

Step 4: Conclusion:
Both the assertion and the reason are factually correct, and the reason accurately explains the assertion. The combination of sex chromosomes determines a child's sex, with the father's Y chromosome resulting in a male, and its absence (XX) resulting in a female.