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Assertion (A) : A piece of… (Class 12 Biology 2025, Q16)

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BiologyCBSE Class 12 · Board exam 2025, set 57/7/1 · 1 mark · Assertion-reason

CBSE Class 12 Biology 2025: question 16

Set in the CBSE Class 12 board exam of 2025, paper 57/7/1, section A, question 16, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q16 · 1 mark · Assertion-reasonCompetency-basedBiotechnology: Principles and Processes

Assertion (A) : A piece of DNA inserted into an alien organism generally does not replicate, if not inserted into a chromosome.
Reason (R) : Chromosomes have specific sequences called 'ori' region, where DNA replication is initiated.

  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 2025 board paper, set 57/7/1.

Hints

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

Hint 1

What sequence does replication begin from?

Hint 2

Why must foreign genes be carried on a vector?

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. Foreign DNA can replicate only if it is linked to an origin of replication (ori), such as that present in chromosomes or vectors.

  2. Both statements are true, and R explains A. Hence (A).

    1 mark

Answer: (A)

Where the marks are

  • Both true and R explains A (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Biotechnology: Principles and Processes, one at a time, marked against the answer key and marking points.Back to the full paper2025 board paper, set 57/7/1: 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.