UPSC Prelims 2025 Q49: Science & Technology – Health & Diseases
- (a) Only one
- (b) Only two
- (c) All the three
- (d) None
Answer: (d) None
Explanation
Statement-by-Statement Breakdown:
| Statement | Claim | Reality | Verdict |
|---|---|---|---|
| I | No virus can survive in ocean waters | Oceans contain an estimated 10³¹ viral particles - the most virus-dense environment on Earth | FALSE |
| II | No virus can infect bacteria | Bacteriophages (phages) are viruses that specifically infect bacteria - among the most abundant organisms on Earth | FALSE |
| III | No virus can change cellular transcriptional activity in host cells | Many viruses actively hijack host transcription - HIV inserts DNA into host genome, influenza shuts down host transcription, herpes viruses redirect cellular machinery | FALSE |
All three statements are false — answer is None.
Key facts:
Marine viruses kill ~20% of ocean bacteria daily — critical regulators of marine ecosystems.
Bacteriophages are being revived as phage therapy — an antibiotic alternative for drug-resistant infections.
HIV reverse transcription followed by integration into host DNA is a textbook example of viral manipulation of host transcription.
Answer: (d) None.
Why each option is right or wrong
- (a) Incorrect. All three statements are false, not just one. Viruses are the most abundant biological entities in the ocean.
- (b) Incorrect. All three are false, not just two. Bacteriophages — viruses that infect bacteria — are among the most studied organisms in microbiology.
- (c) Incorrect. All three statements contradict well-established microbiology — none can be correct.
- (d) CORRECT. All three statements are false. Viruses thrive in oceans (10³¹ particles), bacteriophages infect bacteria, and viruses routinely alter host cell transcription to replicate.
Key point
All three are FALSE. Oceans = most virus-rich environment. Bacteriophages = viruses that infect bacteria. Viruses routinely hijack host cell transcription (HIV, influenza, herpes).
Remember
ALL THREE are false. Viruses survive in oceans. Bacteriophages infect bacteria. Viruses hijack host transcription (e.g., HIV).
Common mistakes
- Not knowing oceans teem with viruses — marine viruses are critical regulators of marine ecosystems, killing bacteria and recycling nutrients at massive scale.
- Forgetting bacteriophages (phages) — viruses infecting bacteria are among the most numerous entities on Earth and are increasingly relevant as antibiotic alternatives.
- Thinking viruses are passive parasites. Many actively manipulate host transcription machinery to block immune detection and optimise replication.
Exam tip
Virus facts that counter assumptions: Oceans = most virus-dense environment on Earth. Bacteriophages = viruses that infect bacteria (used in phage therapy). HIV = inserts DNA into host genome (permanently alters transcription). UPSC uses triple-false formats to test confident wrong assumptions.
Sources
- NCERT Class XI — Biology (Viruses)
- WHO — Virology Fundamentals
- Nature — Marine Viruses and Their Role in Ocean Ecosystems