RNA and DNA virus
The genetic material of a virus can be either DNA or RNA. The viruses that contain DNA as their genetic material are called the DNA viruses. RNA viruses, on the other hand, contain RNA as their genetic material. The main difference between DNA and RNA viruses is that DNA viruses contain large genomes due to the accurate replication whereas RNA viruses contain small genomes due to the error-prone replication.
What are DNA Viruses?
- The genetic information of DNA viruses is stored in the form of DNA.
- Few may contain single-stranded DNA in their genome.
- Some DNA viruses may also contain an envelope.
Seven classes of viruses can be identified based on the type of genetic material present in each virus and their method of replication. This classification is called the Baltimore classification
Classes of DNA Viruses
| Class | Types of Nucleic Acids | Family | Biosynthesis |
| Class-I | Double stranded linear DNA | Adenoviridae (Non-Enveloped) | Cellular enzymes transcribes viral DNA in nucleus in Adenoviridae and Herpesviridae |
| Herpesviridae (Enveloped) | |||
| Poxviridae (Enveloped) | |||
| Class-II | Single stranded linear DNA(sense strand) | Parvoviridae | Cellular enzymes transcribes viral DNA in nucleus |
| Class-VII | Double stranded circular DNA | Papovaviridae (non-enveloped)
|
Cellular enzymes transcribes viral DNA in nucleus in Papovaviridae. |
| Hepadnaviridae (enveloped) |
Classes of RNA Viruses
| Class | Types of Nucleic Acids | Family | Biosynthesis |
| Class-III | Double stranded RNA | Reoviridae (double capsid, non-enveloped) | Viral enzymes copies antisense RNA to make mRNA in the cytoplasm |
| Class-IV | Single stranded (Sense strand) | Picornaviridae (non-enveloped) | Viral RNA functions as a template for synthesis of RNA polymerase which copies antisense strand RNA to make mRNA in cytoplasm |
| Togaviridae (enveloped) | |||
| Class-V | Single stranded (Anti-sense strand) | Rhabdoviridae (enveloped) | Viral enzymes copies viral RNA to make mRNA in cytoplasm |
| Class-VI | Single stranded (Sense strand) Reverse Transcriptase (RNA dependent DNA polymerase) | Reteroviridae | Viral enzyme copies viral RNA to make DNA in cytoplasm; DNA moves to nucleus |