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Biology · 2025 · 2 marks
CBSE 2025 · Region 4 · Set 1 · Q17
(a) Explain how the immunity of a person is affected if there is atrophy (degeneration) of the thymus gland at an early stage of life.
(a)
Explain how the immunity of a person is affected if there is atrophy (degeneration) of the thymus gland at an early stage of life.
OR
(b)(i)
What are interferons ? Explain their role in providing immunity to a person.
(ii)
Which category of innate immunity defence barrier can interferons be classified into ?
Marking-scheme solution
(a)
The immunity will decrease.
Immature lymphocytes will not differentiate into antigen – sensitive
lymphocytes / development and maturation of T-lymphocytes does not take place.
OR
(b)(i)
• Virus infected cells secrete proteins called interferons.
• Interferons protect non-infected cells from further viral infection
(ii)
Cytokine barriers.
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CBSE Class 12 Biology past-paper question from the 2025 board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.