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Answer the following. (Class 12 Biology 2026, Q20b)

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BiologyCBSE Class 12 · Board exam 2026, set 57/1/1 · 2 marks · Very short answer

CBSE Class 12 Biology 2026: question 20(b)

Set in the CBSE Class 12 board exam of 2026, paper 57/1/1, section B, question 20(b), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q20(b) · 2 marks · Very short answerMolecular Basis of Inheritance

Answer the following.

  1. (i)

    Differentiate between a DNA and RNA nucleotide.

    1 mark
  2. (ii)

    Name the two types of bonds present within a single nucleotide.

    1 mark

Source: official question paper from cbse.gov.in (PDF). See it in the full 2026 board paper, set 57/1/1.

Hints

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

Hint 1

A nucleotide has three parts: base, sugar and phosphate. Compare the sugar and the bases.

Hint 2

Name the bond joining base to sugar, then the bond joining sugar to phosphate.

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. (i) A DNA nucleotide contains deoxyribose sugar and one of the bases A, G, C or T. An RNA nucleotide contains ribose sugar and one of the bases A, G, C or U (uracil in place of thymine).

    1 mark

  2. (ii) N-glycosidic linkage, between the nitrogen base and the pentose sugar (C-1').

    ½ mark

  3. Phosphoester linkage, between the phosphate group and the 5'-OH of the sugar.

    ½ mark

Answer: (i) DNA nucleotide: deoxyribose with T; RNA nucleotide: ribose with U; (ii) N-glycosidic bond and phosphoester bond

Where the marks are

  • Any one correct difference (sugar or base) (1 mark)
  • N-glycosidic linkage (½ mark)
  • Phosphoester linkage (½ 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 paper2026 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.