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Answer the following… (Class 12 Biology 2025, Q31A)

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BiologyCBSE Class 12 · Board exam 2025, set 57/1/1 · 5 marks · Long answer

CBSE Class 12 Biology 2025: question 31(A)

Set in the CBSE Class 12 board exam of 2025, paper 57/1/1, section E, question 31(A), for 5 marks. Try it first; the hints and our step-by-step solution are below.

Q31(A) · 5 marks · Long answerHuman Health and Disease

Answer the following questions :

  1. (i)

    State what do you understand by "MALT" ? Where it is located inside our body ?

    0 marks
  2. (ii)

    Explain cytokine barriers.

    0 marks
  3. (iii)

    Name the diagnostic test for AIDS. On what principle does it work ?

    0 marks
  4. (iv)

    Bone marrow and thymus play an important role in human immune system. Explain how are they able to achieve this.

    0 marks

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

MALT is lymphoid tissue found in the moist linings of body passages.

Hint 2

Cytokine barrier proteins are made by virus-infected cells. Name them.

Hint 3

Which organ produces lymphocytes, and where do T-cells mature?

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) MALT stands for Mucosa-Associated Lymphoid Tissue. It makes up about 50% of the lymphoid tissue in the human body.

    ½ mark

  2. It is located within the lining of the major tracts: the respiratory, digestive and urogenital tracts.

    ½ mark

  3. (ii) Cytokine barriers: Virus-infected cells secrete proteins called interferons. These protect neighbouring non-infected cells from further viral infection.

    1 mark

  4. (iii) The diagnostic test for AIDS is ELISA (Enzyme Linked Immuno-Sorbent Assay).

    1 mark

  5. It works on the principle of antigen–antibody interaction, detecting the antibodies produced against HIV. (PCR, based on amplification of the viral nucleic acid, is also accepted.)

    1 mark

  6. (iv) Bone marrow and thymus are primary lymphoid organs. Bone marrow produces all blood cells, including lymphocytes. Some lymphocytes migrate to the thymus, where they mature into T-lymphocytes. Together, these organs provide the micro-environment in which immature lymphocytes develop and differentiate into antigen-sensitive lymphocytes.

    1 mark

Answer: (i) Mucosa-Associated Lymphoid Tissue, in the lining of the respiratory, digestive and urogenital tracts; (ii) interferons from virus-infected cells protect uninfected cells; (iii) ELISA, based on antigen–antibody interaction; (iv) they produce lymphocytes and provide the micro-environment for their development and maturation into antigen-sensitive cells.

Where the marks are

  • Full form of MALT (½ mark)
  • Location in the lining of the major tracts (½ mark)
  • Interferons from virus-infected cells protect non-infected cells (1 mark)
  • Names ELISA (1 mark)
  • Principle: antigen–antibody interaction (1 mark)
  • Bone marrow/thymus provide the micro-environment for lymphocyte development and maturation (1 mark)

Revise the chapter

Practise this chapterBoard-style questions from Human Health and Disease, 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.