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Assertion (A) : Linked genes… (Class 12 Biology 2024, Q14)

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

CBSE Class 12 Biology 2024: question 14

Set in the CBSE Class 12 board exam of 2024, paper 57/1/1, section A, question 14, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q14 · 1 mark · Assertion-reasonCompetency-basedPrinciples of Inheritance and Variation

Assertion (A) : Linked genes do not show dihybrid F ratio 9 : 3 : 3 : 1.
Reason (R) : Linked genes do not undergo independent assortment.

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

Source: official question paper from cbse.gov.in (PDF). See it in the full 2024 board paper, set 57/1/1.

Hints

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

Hint 1

The 9:3:3:1 ratio depends on one of Mendel's laws.

Hint 2

Which law fails for genes on the same chromosome?

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. Linked genes lie on the same chromosome, so they do not assort independently. They are inherited together, giving mostly parental combinations.

    ½ mark

  2. Because there is no independent assortment, the 9:3:3:1 ratio is not obtained. Both statements are true, and R correctly explains A.

    ½ mark

Answer: (A)

Where the marks are

  • Both true and R explains A (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 57/1/1: 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.