UPSC Prelims 2025 · Question 9 of 100

UPSC Prelims 2025 question on Viruses in Oceans and Bacteria

Consider the following statements:

I. No virus can survive in ocean waters.

II. No virus can infect bacteria.

III. No virus can change the cellular transcriptional activity in host cells.

How many of the statements given above are correct?

  1. Only one
  2. Only two
  3. All the three
  4. None
Show answer

Answer: D. None

Analysis

None of the statements are correct → Option (d).

Statement by statement

Statement I – INCORRECT: Viruses are abundant and active in ocean waters. Marine viruses, particularly bacteriophages (viruses that infect bacteria), are the most numerous biological entities in the ocean. They play a crucial role in regulating microbial populations and nutrient cycles. Studies have shown that viruses can survive in seawater for extended periods.

Statement II – INCORRECT: This statement is inaccurate. Bacteriophages, or phages, are viruses that specifically infect and replicate within bacterial cells. They are ubiquitous in environments where bacteria are present, including soil, water, and the human body.

Statement III – INCORRECT: Viruses can and often do alter the transcriptional activity of their host cells. Upon infection, many viruses manipulate the host's gene expression machinery to favor viral replication and suppress host defenses. Certain viral proteins can interact with host transcription factors, leading to changes in gene expression.

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