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Assertion (A) : Synthetic… (Class 12 Biology 2023, Q14)

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BiologyCBSE Class 12 · Board exam 2023, set 57/5/1 · 1 mark · Assertion-reason

CBSE Class 12 Biology 2023: question 14

Set in the CBSE Class 12 board exam of 2023, paper 57/5/1, 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-basedBiotechnology: Principles and Processes

Assertion (A) : Synthetic oligonucleotide polymers are used during Annealing in a PCR.
Reason (R) : The primers bind to the double stranded DNA at their complementary regions.

  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 57/5/1.

Hints

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

Hint 1

Think about what happens to the DNA in the denaturation step just before annealing.

Hint 2

Is the template double-stranded when the primers bind?

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. The primers used in annealing are synthetic oligonucleotides, so (A) is true.

    ½ mark

  2. Primers bind to single-stranded, denatured DNA, not to double-stranded DNA, so (R) is false. Hence option (C).

    ½ mark

Answer: (C)

Where the marks are

  • A true, R false (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 paper2023 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.