Q.12 Which family of viruses has single stranded DNA?
(A) Herpesviridae (B) Poxviridae (C) Retroviridae (D) Parvoviridae
Parvoviridae is the family of viruses with single-stranded DNA.
Option Analysis
Herpesviridae viruses, such as herpes simplex virus, contain double-stranded DNA genomes enclosed in an icosahedral capsid with a lipid envelope. Poxviridae viruses, like the one causing smallpox, possess large double-stranded DNA genomes and replicate in the host cell cytoplasm using their own enzymes. Retroviridae viruses carry single-stranded RNA genomes that reverse transcribe into DNA via reverse transcriptase after infection. Parvoviridae viruses uniquely feature linear single-stranded DNA genomes, typically 4-6 kb long, making them small and dependent on host cell replication machinery.
Correct Answer
(D) Parvoviridae stands out as the only family among the options with single-stranded DNA.
The Parvoviridae family represents the primary group of viruses with single stranded DNA genomes, distinguishing it from other DNA or RNA virus families. This characteristic enables unique replication strategies reliant on host nuclear machinery. Understanding which family of viruses has single stranded DNA proves essential in molecular biology, biotechnology, and virology studies.
Key Characteristics of Single Stranded DNA Viruses
Single stranded DNA viruses like those in Parvoviridae possess linear ssDNA genomes, often negative-sense, requiring conversion to double-stranded forms for replication. Parvoviruses infect mammals and birds, causing diseases such as canine parvovirus in veterinary contexts. Their small size (18-26 nm) and lack of envelope facilitate environmental stability.
Detailed Breakdown of Options
| Virus Family | Genome Type | Key Examples | Replication Site |
|---|---|---|---|
| Herpesviridae | Double-stranded DNA | Herpes simplex, Varicella-zoster | Host nucleus |
| Poxviridae | Double-stranded DNA | Smallpox, Vaccinia | Host cytoplasm |
| Retroviridae | Single-stranded RNA | HIV, HTLV | Host cytoplasm (reverse transcription) |
| Parvoviridae | Single-stranded DNA | Parvovirus B19, AAV | Host nucleus |
Herpesviridae features enveloped, icosahedral virions with large dsDNA (120-240 kb) driving latent infections. Poxviridae stands apart with complex brick-shaped virions and cytoplasmic factories for dsDNA replication. Retroviridae relies on RNA intermediates and integrase for proviral DNA insertion, not native ssDNA.
Biological Significance
Parvoviridae’s ssDNA genome supports applications in gene therapy, notably adeno-associated virus (AAV) vectors used in biotech research. This family highlights evolutionary adaptations in single stranded DNA virus family dynamics, contrasting dsDNA families’ autonomous replication. Students preparing for exams benefit from recognizing these distinctions in viral classification.
