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Assertion (A) : Human female… (Class 10 Science 2024, Q18)

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ScienceCBSE Class 10 · Board exam 2024, set 31/2/1 · 1 mark · Assertion-reason

CBSE Class 10 Science 2024: question 18

Set in the CBSE Class 10 board exam of 2024, paper 31/2/1, 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) : Human female has a perfect pair of sex chromosome.
Reason (R) : Sex chromosome contributed by the human male in the zygote decides the sex of a child.

  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 2024 board paper, set 31/2/1.

Hints

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

Hint 1

Write the sex chromosomes of males and females.

Hint 2

Does R give the reason for A, or is it a separate fact?

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. (A) is true: females have a perfect pair of sex chromosomes, XX.

    ½ mark

  2. (R) is true: the X or Y from the father decides the sex of the child. But this does not explain why the female has XX. Option (B) is correct.

    ½ mark

Answer: Option (B)

Where the marks are

  • Selects option (B) (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 paper2024 board paper, set 31/2/1: 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.