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(i) Explain the convention… (Class 12 Biology 2024, Q27b)

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BiologyCBSE Class 12 · Board exam 2024, set 57/1/1 · 3 marks · Short answer

CBSE Class 12 Biology 2024: question 27(b)

Set in the CBSE Class 12 board exam of 2024, paper 57/1/1, section C, question 27(b), for 3 marks. Try it first; the hints and our step-by-step solution are below.

Q27(b) · 3 marks · Short answerBiotechnology: Principles and Processes

(i) Explain the convention for naming EcoRI. (2)
(ii) With the help of an illustration only, show the action of EcoRI on a DNA Polynucleotide. (1)

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 name is built from the genus, species and strain of the bacterium it comes from.

Hint 2

EcoRI's recognition site reads the same on both strands in the 5'→3' direction: G-A-A-T-T-C.

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) EcoRI is isolated from Escherichia coli strain RY13. E stands for the genus Escherichia.

    ½ mark

  2. (i) co stands for the species coli.

    ½ mark

  3. (i) R stands for the strain RY13.

    ½ mark

  4. (i) I (Roman numeral) shows the order in which the enzyme was isolated from that strain; EcoRI was the first.

    ½ mark

  5. (ii) EcoRI recognises the palindrome
    –G A A T T C–
    –C T T A A G–
    and cuts each strand between G and A.

    ½ mark

  6. (ii) Products:
    –G AATTC–
    –CTTAA G–
    This leaves single-stranded overhanging sticky ends (AATT).

    ½ mark

Answer: (i) E – Escherichia (genus), co – coli (species), R – strain RY13, I – first enzyme isolated from that strain; (ii) EcoRI cuts GAATTC between G and A, giving sticky ends

Where the marks are

  • Meaning of E, co, R and I (½ × 4 marks)
  • Shows palindromic recognition sequence GAATTC (½ mark)
  • Shows cut between G and A producing sticky ends (½ 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 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.