Consider the following statements:
- Adenoviruses have single-stranded DNA genomes whereas retroviruses have double-stranded DNA genomes.
- Common cold is sometime caused by an adenovirus whereas AIDS is caused by a retrovirus.
Which of the statements given above is/are correct?
Detailed Explanation:
Answer: Option 2 — 2 Only
Statement 1 is incorrect because adenoviruses have double-stranded DNA genomes, not single-stranded DNA. Retroviruses have single-stranded RNA genomes (not double-stranded DNA), which they reverse-transcribe into DNA using reverse transcriptase. Statement 2 is correct as adenoviruses are a common cause of the common cold, and AIDS is indeed caused by HIV, a retrovirus.
❌ Statement 1 – Incorrect: Adenoviruses have double-stranded DNA genomes; retroviruses have single-stranded RNA genomes, not double-stranded DNA.
✅ Statement 2 – Correct: The common cold can be caused by adenoviruses, and AIDS is caused by HIV, which is a retrovirus.
📝 Short Notes: Viral Genome Types
| Virus Type | Genome Structure | Examples | Key Characteristics |
|---|---|---|---|
| Adenoviruses | Double-stranded DNA (dsDNA) | Common cold, conjunctivitis | Non-enveloped, icosahedral structure |
| Retroviruses | Single-stranded RNA (ssRNA) | HIV (AIDS), HTLV | Use reverse transcriptase to convert RNA to DNA |
| Orthomyxoviruses | Single-stranded RNA (ssRNA) | Influenza virus | Enveloped, segmented genome |
| Herpesviruses | Double-stranded DNA (dsDNA) | Herpes simplex, Varicella-zoster | Enveloped, large genome, latency |
- DNA Viruses: Generally replicate in the nucleus using host cell machinery (exceptions: poxviruses replicate in cytoplasm)
- RNA Viruses: Most replicate in the cytoplasm; carry their own RNA polymerase
- Retroviruses: Unique in possessing reverse transcriptase enzyme that synthesizes DNA from RNA template
- Common Cold Causes: Rhinoviruses (most common), coronaviruses, adenoviruses, and others
- HIV Classification: Lentivirus genus of the Retroviridae family; targets CD4+ T cells
Question 1 of 6 Communicable Diseases
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