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Biology

Class 12 · Science & Environment

Ch 5 · Molecular Basis of Inheritance

Real UPSC Prelims questions from 2016–2026, linked to this book. Try each one first, then open the answer. 2026 answers follow UPSC's provisional answer key.

Prelims 2016 · Q59

Which of the following statements is/are correct?

Viruses can infect

  1. 1.bacteria
  2. 2.fungi
  3. 3.plants

Select the correct answer using the code given below.

  1. (a)1 and 2 only
  2. (b)3 only
  3. (c)1 and 3 only
  4. (d)1, 2 and 3
Show answer

UPSC's answer: (d)

NCERT answers it: Class 12 Biology, Ch 5 (Molecular Basis of Inheritance); Class 12 Biology, Ch 8 (Microbes in Human Welfare).

The one fact NCERT doesn't give: Some viruses, called mycoviruses, infect fungi.

Class 12 Biology: bacteriophages are viruses that infect bacteria (ch 5), and ch 8 names plant viruses. With the fact, all three are true. Answer (d).

Hindi version: UPSC's official question paper (2016), question 59 ↗

Prelims 2023 · Q70

'Microsatellite DNA' is used in the case of which one of the following?

  1. (a)Studying the evolutionary relationships among various species of fauna
  2. (b)Stimulating 'stem cells' to transform into diverse functional tissues
  3. (c)Promoting clonal propagation of horticultural plants
  4. (d)Assessing the efficacy of drugs by conducting series of drug trials in a population
Show answer

UPSC's answer: (a)

NCERT answers it: Class 12 Biology, Ch 5 (Molecular Basis of Inheritance).

How to solve it with NCERT: Class 12 Biology, ch 5: microsatellites are repetitive DNA sequences used in determining population and genetic diversities. Of the options, only (a) is about comparing the genes of living things. Answer (a).

Hindi version: UPSC's official question paper (2023), question 70 ↗

Prelims 2025 · Q49

Consider the following statements:

  1. I.No virus can survive in ocean waters.
  2. II.No virus can infect bacteria.
  3. III.No virus can change the cellular transcriptional activity in host cells.

How many of the statements given above are correct?

  1. (a)Only one
  2. (b)Only two
  3. (c)All the three
  4. (d)None
Show answer

UPSC's answer: (d)

NCERT answers it: Class 12 Biology, Ch 5 (Molecular Basis of Inheritance).

The one fact NCERT doesn't give: Seawater holds huge numbers of viruses, so statement I is false as well.

Class 12 Biology, ch 5: bacteriophages are viruses that infect bacteria (II false). An infected bacterium makes virus particles from the viral genes as if they were its own, so the virus changes its host's activity (III false). With the fact, none is correct. Answer (d).

Hindi version: UPSC's official question paper (2025), question 49 ↗

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