Question 30 from UPSC CSE 2025 - Basic Science

Question

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?

Accepted Answer

Correct Option: D. None of the above statements is correct

Strategy: Each statement contains an absolute—'no virus can...'—making them extreme assertions. Recall basic virology: many viruses exist in ocean water, some viruses infect bacteria (bacteriophages), and viral infections often alter host cell transcription. Thus, all three statements are categorically false, so none can be correct.

Key Info: Viruses are acellular infectious agents that require living host cells to replicate. They are found in nearly every environment on Earth, including extreme habitats such as deep ocean waters, where they exert profound impacts on microbial dynamics and nutrient cycling. Marine viruses are especially abundant, with populations estimated in the order of 10^30 globally, and include various bacteriophages and viruses infecting protists and other marine organisms.

Some viruses, notably bacteriophages, specifically infect bacteria and can play a crucial ecological role by regulating bacterial populations, facilitating gene transfer, and influencing microbial evolution. Bacteriophages are being researched and used for phage therapy due to their specificity in targeting pathogenic bacteria.

Viruses commonly alter host cell activity: upon infection, they often modify the host cell's gene expression, co-opting transcriptional and translational machinery to facilitate replication of viral nucleic acids and proteins. This process frequently results in the suppression or alteration of host defenses, cell cycle regulation, or other aspects of cellular function. These effects are well-documented in both DNA and RNA viruses across a wide variety of host organisms.

Answer

Option A: Only one

Answer

Option B: Only two

Answer

Option C: All three

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?

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?