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Assertion (A) : In birds the… (Class 12 Biology 2024, Q15)

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BiologyCBSE Class 12 · Board exam 2024, set 57/5/1 · 1 mark · Assertion-reason

CBSE Class 12 Biology 2024: question 15

Set in the CBSE Class 12 board exam of 2024, paper 57/5/1, section A, question 15, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q15 · 1 mark · Assertion-reasonCompetency-basedPrinciples of Inheritance and Variation

Assertion (A) : In birds the sex of the offspring is determined by males.
Reason (R) : Males are homogametic while females are heterogametic.

  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 57/5/1.

Hints

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

Hint 1

Recall the ZW system.

Hint 2

The heterogametic sex determines the sex of the offspring.

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. In birds, females are ZW (heterogametic) and males are ZZ (homogametic). The reason is therefore true.

  2. Because the female produces two kinds of eggs, the female decides the sex of the offspring. The assertion is false, so the answer is option (D).

    1 mark

Answer: (D)

Where the marks are

  • (A) false, (R) true due to the ZW system (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Principles of Inheritance and Variation, one at a time, marked against the answer key and marking points.Back to the full paper2024 board paper, set 57/5/1: 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.