Prelims 2021

Q. Consider the following statements:

1. Adenoviruses have single-stranded DNA genomes whereas retroviruses have double-stranded DNA genomes.
2. Common cold is sometimes 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
c) Both 1 and 2
d) Neither 1 nor 2
Correct Answer: b) 2 only

Question from UPSC Prelims 2021 GS Paper

Explanation : 

Adenoviruses and Retroviruses

The virology field often categorizes viruses based on their genetic material and replication methods. A common misconception is that adenoviruses have single-stranded DNA genomes, while it is actually the opposite. Adenoviruses are known for their double-stranded DNA genomes. They can infect various body systems, including the respiratory tract and nervous system.

Contrastingly, retroviruses are equipped with single-stranded RNA genomes. They utilize an enzyme known as reverse transcriptase to transcribe their RNA into DNA, which is then incorporated into the host’s genome. Although the resulting DNA is double-stranded, the retrovirus’s original genome is RNA.

Viruses and Diseases: Common Cold and AIDS

The common cold can be attributed to various viruses, including adenoviruses, in addition to rhinoviruses and coronaviruses. These viruses can cause respiratory symptoms akin to those of the common cold.

In the case of AIDS (Acquired Immunodeficiency Syndrome), the culprit is the human immunodeficiency virus (HIV), which is a retrovirus. HIV is notorious for attacking the immune system, leading to AIDS when not properly managed.

The statement about adenoviruses having single-stranded DNA is incorrect, while the association of the common cold with adenoviruses and AIDS with a retrovirus is correct. Therefore, “2 only” is the accurate answer.

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