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A patient with ADA… (Class 12 Biology 2025, Q21A)

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BiologyCBSE Class 12 · Board exam 2025, set 57/1/1 · 2 marks · Very short answer

CBSE Class 12 Biology 2025: question 21(A)

Set in the CBSE Class 12 board exam of 2025, paper 57/1/1, section B, question 21(A), for 2 marks. Try it first; the hints and our step-by-step solution are below.

Q21(A) · 2 marks · Very short answerBiotechnology and its Applications

A patient with ADA deficiency requires periodic infusion of genetically engineered lymphocytes. Explain why such periodic infusion is required and also suggest a permanent cure for such ADA deficiency.

Source: official question paper from cbse.gov.in (PDF). See it in the full 2025 board paper, set 57/1/1.

Hints

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

Hint 1

Think about the life span of the lymphocytes that are returned to the patient.

Hint 2

For a permanent cure, the corrected gene must be present in cells that keep producing new cells throughout life.

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. Why periodic infusion: Lymphocytes are taken from the patient's blood and given a functional ADA cDNA using a retroviral vector, then returned to the patient. These genetically engineered lymphocytes are not immortal. They die after some time, so the patient needs fresh infusions periodically.

    1 mark

  2. Permanent cure: The gene producing ADA, isolated from marrow cells, can be introduced into cells (lymphocytes or stem cells) at early embryonic stages. All cells arising from them would then carry the functional gene.

    1 mark

Answer: Engineered lymphocytes are not immortal, so periodic infusion is needed; a permanent cure is introducing the ADA gene from marrow cells into cells at early embryonic stages.

Where the marks are

  • Engineered lymphocytes are not immortal / have a limited life span (1 mark)
  • Permanent cure: introduce the ADA gene isolated from marrow cells into early embryonic-stage cells (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Biotechnology and its Applications, one at a time, marked against the answer key and marking points.Back to the full paper2025 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.