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 the sex of a child is determined by the combination of sex chromosomes inherited from both parents. The mother always contributes an X chromosome, while the father can contribute either an X or a Y chromosome. If the child inherits an X chromosome from both parents (XX), the result is female. If the child inherits an X chromosome from the mother and a Y chromosome from the father (XY), the result is male.

Step 2: Understanding the Reason (R):
The reason explains that a male child receives a Y chromosome from the father, while the mother always contributes an X chromosome. The presence of the Y chromosome is the key determinant of the male sex because it carries genes that promote the development of male characteristics, such as the SRY gene, which triggers the development of male reproductive structures.

Step 3: Connecting Assertion (A) and Reason (R):
- The assertion is about the inheritance of sex chromosomes and how the combination of these chromosomes determines the sex of the child. - The reason is explaining the mechanism by which the Y chromosome from the father results in a male child. It also emphasizes the mother’s contribution of only an X chromosome. - The reason is indeed a direct consequence of the assertion, as it elaborates on the genetic basis behind the assertion that the presence of a Y chromosome leads to the male sex.

Step 4: Conclusion:
Both the assertion and the reason are true, and the reason correctly explains the assertion. The sex of a child is determined by the combination of sex chromosomes, with the presence of a Y chromosome from the father resulting in a male and the absence of it (XX) resulting in a female.