Question 69 from UPSC CSE 2021 - Current Affairs

Question

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?

IASCODEX · Accepted Answer

Correct Option: B. 2 only

Strategy: Focus on the genetic material of both viruses. Statement 1 is incorrect: adenoviruses are double-stranded DNA viruses, not single-stranded; retroviruses contain single-stranded RNA, not double-stranded DNA. Statement 2 is correct: adenovirus can cause the common cold, while AIDS is caused by a retrovirus (HIV). Eliminate options with statement 1 correct, select '2 only'.

Key Info: **Adenoviruses**
- **Family:** Adenoviridae
- **Structure:** Non-enveloped, icosahedral viruses
- **Genome:** Linear double-stranded DNA (dsDNA)
- **Associated Illnesses:** They cause various diseases in humans, including respiratory infections (like the common cold), conjunctivitis (pink eye), pharyngitis, pneumonia, and gastroenteritis.
- **Serotypes:** There are over 50 known serotypes of human adenoviruses.

**Retroviruses**
- **Structure:** Enveloped viruses
- **Genome:** Single-stranded RNA
- **Replication:** They replicate via reverse transcription, where an enzyme converts the RNA genome into double-stranded DNA. This DNA then integrates into the host cell's genome.
- **Key Example:** The Human Immunodeficiency Virus (HIV), the causative agent of Acquired Immunodeficiency Syndrome (AIDS), is a retrovirus.

**Additional Notes**
- The common cold can also be caused by other viruses, such as rhinovirus and coronavirus, but adenovirus is a recognized cause.
- Retroviruses do not possess a naturally occurring double-stranded DNA genome; the DNA form is an intermediate created inside the host cell.
- Adenoviruses do not have a single-stranded DNA stage in their natural infection cycle.

IASCODEX · Answer

Option A: 1 only

IASCODEX · Answer

Option C: Both 1 and 2

IASCODEX · Answer

Option D: Neither 1 nor 2

Consider the following statements: Adenoviruses have single-stranded DNA genomes, whereas retroviruses have double-stranded DNA genomes. Common cold is sometimes caused by an adenovirus, whereas AIDS is caused by a retrovirus. Which of the statements given above is/are correct?

Consider the following statements:

Adenoviruses have single-stranded DNA genomes, whereas retroviruses have double-stranded DNA genomes.

Common cold is sometimes caused by an adenovirus, whereas AIDS is caused by a retrovirus.
Which of the statements given above is/are correct?