Science & Tech · Virology Basics & Transmission
The concept being tested: Viral structure and biological properties.
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?
All three statements make a sweeping "no virus can..." claim, and each is contradicted by well-established virology. Oceans are in fact the largest reservoir of viruses on Earth: marine viruses, overwhelmingly bacteriophages that infect marine bacteria and cyanobacteria, number roughly 10 to the power 30 particles and drive nutrient cycling through the so-called viral shunt, so the first statement fails. Bacteriophages are a well-studied class of viruses whose entire host range is bacteria, forming the basis of early molecular biology and modern phage therapy, so the second statement fails too. And many viruses actively hijack host transcriptional machinery, viral proteins such as HIV Tat or adenovirus E1A reprogram RNA polymerase II and host transcription factors to favour viral gene expression, so the third statement fails as well. Since every statement is false, the correct count of correct statements is zero, which is why "None" is the answer.
What UPSC was testing
UPSC built this as a triple-negative, all-false set to see whether aspirants know specific counterexamples, marine viral abundance, bacteriophages, and transcriptional hijacking, rather than assuming an absolute-sounding claim must have at least one true peer among the three.
How often this comes up
This concept has appeared 12 times in UPSC Prelims General Studies Paper I between 2015 and 2025 — in 2015, 2016, 2017, 2019, 2020, 2021, 2022 and 2025.
The option-by-option autopsy for this question — why each of the other three is wrong, and which neighbouring concept each one was built from — is in the app.
Other past-year questions touching Virology Basics & Transmission.