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In the future… (Class 12 Biology SQP 2024-25, Q32B)

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BiologyCBSE Class 12 · Sample paper, session 2024-25 · 5 marks · Long answer

CBSE Class 12 Biology sample paper 2024-25: question 32(B)

From the official CBSE sample question paper for 2024-25, section E, question 32(B), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q32(B) · 5 marks · Long answerCompetency-basedBiotechnology and its Applications

In the future, genetic therapies may be used to prevent, treat, or cure certain inherited disorders in humans. Justify the statement with a suitable example.

Source: official sample paper from cbseacademic.nic.in (PDF). See it in the full Sample paper 2024-25.

Hints

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

Hint 1

Think of the first disorder ever treated by clinical gene therapy in 1990.

Hint 2

The disorder is an immune deficiency caused by a missing enzyme gene. What are the conventional treatments, and why are they not enough?

Hint 3

Describe how lymphocytes are cultured, given a functional cDNA through a retroviral vector and returned to the patient. Then explain why repeated infusions are needed and how a permanent cure could be achieved.

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. Gene therapy is a set of methods that corrects a gene defect diagnosed in a child or embryo. Genes are inserted into a person's cells and tissues to treat a disease.

    ½ mark

  2. Correction means delivering a normal (functional) gene into the individual or embryo, so that it takes over the function of the defective, non-functional gene.

    ½ mark

  3. Example: the first clinical gene therapy was given in 1990 to a 4-year-old girl with adenosine deaminase (ADA) deficiency. The ADA enzyme is essential for the immune system to work.

    ½ mark

  4. This disorder is caused by deletion of the gene that codes for adenosine deaminase.

    ½ mark

  5. Conventional treatments for ADA deficiency are bone marrow transplantation and enzyme replacement therapy, in which functional ADA is injected into the patient.

    ½ mark

  6. Neither of these approaches is completely curative.

    ½ mark

  7. Gene therapy procedure, step 1: lymphocytes are taken from the patient's blood and grown in a culture outside the body.

    ½ mark

  8. Step 2: a functional ADA cDNA is introduced into these lymphocytes using a retroviral vector. The engineered lymphocytes are then returned to the patient.

    ½ mark

  9. These lymphocytes are not immortal, so the patient needs periodic infusions of genetically engineered lymphocytes.

    ½ mark

  10. If the ADA gene isolated from marrow cells is introduced into cells at early embryonic stages, it could give a permanent cure. This justifies the statement that gene therapy may prevent, treat or cure inherited disorders in future.

    ½ mark

Answer: Gene therapy inserts a normal gene to replace or compensate for a defective one. Example: ADA deficiency (1990). The patient's lymphocytes are cultured, given functional ADA cDNA through a retroviral vector and returned to the body, with periodic infusions needed. Introducing the gene at early embryonic stages could give a permanent cure.

Where the marks are

  • Defines gene therapy as correction of a gene defect by inserting genes into cells (0.5 mark)
  • States that a normal gene is delivered to compensate for the non-functional gene (0.5 mark)
  • Names ADA deficiency, the first clinical gene therapy in 1990 on a 4-year-old girl, and the role of ADA in immunity (0.5 mark)
  • States the cause: deletion of the ADA gene (0.5 mark)
  • Mentions bone marrow transplant or enzyme replacement therapy (0.5 mark)
  • Notes that these conventional methods are not completely curative (0.5 mark)
  • Patient's lymphocytes are cultured outside the body (0.5 mark)
  • Functional ADA cDNA is introduced using a retroviral vector and the cells are returned to the patient (0.5 mark)
  • Cells are not immortal, so periodic infusion is needed (0.5 mark)
  • Gene introduced at early embryonic stage could give a permanent cure (0.5 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 paperSample paper 2024-25: 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.