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Assertion (A) : Genes… (Class 10 Science 2023, Q18)

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ScienceCBSE Class 10 · Board exam 2023, set 31/1/1 · 1 mark · Assertion-reason

CBSE Class 10 Science 2023: question 18

Set in the CBSE Class 10 board exam of 2023, paper 31/1/1, section A, question 18, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q18 · 1 mark · Assertion-reasonCompetency-basedHeredity

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.

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

Source: official question paper from cbse.gov.in (PDF). See it in the full 2023 board paper, set 31/1/1.

Hints

Open one hint at a time and try again before the next.

Hint 1

Write the sex chromosomes of the mother and the father.

Hint 2

Which parent must give the Y chromosome to a son?

Step-by-step solution

Each step shows the marks it earns, as an examiner would award them. Checked by an independent re-solve from the question paper.

  1. Sex is decided by the sex chromosome inherited from the parents: XX gives a girl, XY gives a boy. So (A) is true.

  2. A boy (XY) gets his Y chromosome from his father and his X chromosome from his mother. So (R) is false, and the answer is (C).

    1 mark

Answer: Option (C)

Where the marks are

  • A true and R false (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Heredity, one at a time, marked against the answer key and marking points.Back to the full paper2023 board paper, set 31/1/1: every question, by section.

The question is transcribed from the official paper; figures are described in words. The solution, hints and chapter tag are ours. Spotted an error? Write tosupport@questionbuddy.in.