Assertion (A): Genes inherited from the parents decide the sex of a child.

Reason (R): X chromosome in a male child is inherited from his father.

Heredity

Sex Determination

Options

(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.

Official Answer

The correct option is (c): (A) is true, but (R) is false.

sex determinationX chromosomeY chromosomegenetically determined

Marking Scheme

1Stating that Assertion is true because sex is genetically determined in humans (0.5 marks)
2Stating that Reason is false because a male child inherits his X chromosome from his mother (0.5 marks)

Hint

Think about the sex chromosomes of a male ( $XY$ ). From which parent does he get the $Y$ chromosome, and from which does he get the $X$ chromosome?

Quick Oral Answer

The sex of a child is determined by the father because if the sperm carrying the Y chromosome fertilizes the egg, it results in a boy (XY), and if the sperm carrying the X chromosome fertilizes the egg, it results in a girl (XX).

Analysis & Explanation

Assertion (A) is true: In human beings, the sex of an individual is genetically determined by the chromosomes/genes inherited from the parents.

Reason (R) is false: A male child has the sex chromosome combination $XY$ . He inherits the $Y$ chromosome from his father and the $X$ chromosome from his mother. Therefore, the $X$ chromosome in a male child is always inherited from his mother, not his father.

Common Mistakes

1Confusing which parent contributes the X chromosome to a male child.
2Assuming that the father contributes the X chromosome to a son.

Interesting Facts

In humans, the father's sperm determines the sex of the baby because sperm can carry either an X or a Y chromosome, while the mother's egg always carries an X chromosome.

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Frequently Asked Questions

How many marks does this question carry in CBSE Class 10 Science 2023?

This question carries 1 mark in the CBSE Class 10 Science 2023 examination.

Which chapter does this question come from in Science?

This question is from the chapter "Heredity" in the CBSE Class 10 Science syllabus.

What topic does this question cover in Science?

This question covers the topic "Sex Determination" from CBSE Class 10 Science.

What type of question is this in the CBSE Class 10 Science 2023 paper?

This is a MCQ question from Section A in the CBSE Class 10 Science 2023 paper.