Skip to content

The initiation step… (Class 12 Biology SQP 2026-27, Q5)

questionbuddy.in/q/cbse-12-biology-2026-27-sqp-q5-initiation-step-during-process-transcription

BiologyCBSE Class 12 · Sample paper, session 2026-27 · 1 mark · MCQ

CBSE Class 12 Biology sample paper 2026-27: question 5

From the official CBSE sample question paper for 2026-27, section A, question 5, for 1 mark. Try it first; the hints and our step-by-step solution are below.

Q5 · 1 mark · MCQMolecular Basis of Inheritance

The initiation step during the process of transcription in bacteria is shown below. Identify A, B, C and D by selecting the option:

  1. (A)A-RNA polymerase, B-Promoter, C-Sigma factor, D-DNA helix
  2. (B)A-Promoter, B-Sigma factor, C-RNA polymerase, D-DNA helix
  3. (C)A-Promoter, B-RNA polymerase, C-DNA helix, D-Sigma factor
  4. (D)A-Promoter, B-RNA polymerase, C-Sigma factor, D-DNA helix

Figure in the paper: DNA double helix with 3' and 5' ends labelled on both strands; an oval structure (B) bound near the left end with a smaller circle marked sigma (C) on it; A points to the left DNA region where the strands are separated (yellow); D points to the DNA helix at the right. See it in the official paper.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2026-27.

Hints

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

Hint 1

The small circle marked σ is attached to the large enzyme.

Hint 2

Think about where the enzyme binds to start transcription.

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. Transcription initiation in bacteria works as follows: RNA polymerase (B), with its sigma factor (C) attached, binds at the promoter (A), where the strands open. The rest of the molecule is the DNA helix (D).

  2. This gives A – Promoter, B – RNA polymerase, C – Sigma factor, D – DNA helix. Option (D).

    1 mark

Answer: (D)

Where the marks are

  • Correctly labels the promoter, RNA polymerase, sigma factor and DNA helix (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Molecular Basis of Inheritance, one at a time, marked against the answer key and marking points.Back to the full paperSample paper 2026-27: 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.