Consider the following statements : 1. Adenoviruses have single-stranded DNA genomes whereas retroviruses have double-stranded DNA genomes. 2. Common cold is sometime caused by an adenovirus whereas AIDS is caused by a retrovirus. Which of the statements given above is/are correct?
- (a) 1 only
- (b) 2 only ✓ UPSC's answer
- (c) Both 1 and 2
- (d) Neither 1 nor 2
Why the answer is (b)
• Statement 1 is wrong: adenoviruses have double-stranded DNA genomes, while retroviruses (e.g. HIV) have single-stranded RNA genomes that are reverse-transcribed into DNA inside the host cell.
• Statement 2 is correct: adenoviruses cause some common colds (along with rhinoviruses and coronaviruses), and AIDS is caused by HIV, a retrovirus.
• Adenoviruses' DNA stability is why they are used as vaccine vectors (Covishield, Sputnik V).
• Hence 2 only, option (b).
Why the other options are wrong
- (a) 1 only
- Statement 1 is wrong: adenoviruses are dsDNA, retroviruses are ssRNA.
- (c) Both 1 and 2
- Statement 1 is wrong.
- (d) Neither 1 nor 2
- Statement 2 is correct: adenovirus colds and retroviral AIDS.
Asked in the GS Paper I of the UPSC Civil Services Preliminary Examination 2021, held on 10 October 2021. Question and answer key: Union Public Service Commission. Explanation: UPSC Answer Check.