- Viruses can be classified in a number of different ways in order to highlight the nature of their genome, the geometry of their capsid, whether they possess an lipid envelope, or their tropism for a particular tissue type.
- Viral genomes are first categorized by their chemical composition as either DNA or RNA genomes. The headings of the sections below are interlinks which will list viruses within that category.
- DNA Viruses
- dsDNA Viruses: dsDNA genomes possess two anti-parallel strands in a double-helix structure
- ssDNA Viruses: ssDNA genomes possess only a single strand and do not form a double-helix structure
- RNA Viruses
- dsRNA Viruses: dsRNA genomes possess two anti-parallel strands much like DNA in a double-helix-like structure
- ssRNA Viruses: ssRNA genomes possess only a single strands which can be organized in different orientations
- Positive ssRNA Viruses: Orientation of genes in the RNA genome is such that they can be directly translated to proteins much like a host cell's mRNA
- Negative ssRNA Viruses: Orientation of genes in the RNA genome is reversed such that they must be first replicated to the positive RNA strand prior to protein translation
- Retroviruses: These are RNA viruses whose genome must first be "Reverse-transcribed" to DNA and only then transcribed and translated.
|Capsid Geometry Classification|
- As discussed in Viral Structure, viral capsids are highly ordered protein shells which possess specific geometries that can be used for classification
- Icosahedral Viruses: Capsid is an Icosahedron which possesses twenty faces of equilateral triangles
- Helical Viruses: Capsid is arranged as a long helix
- Complex Viruses: Capsid has a complex shape that does not fall into the above categories
|Possession of an Envelope|
- Nonenveloped Viruses: Do not possess an outer lipid envelope
- Enveloped Viruses: Possess an outer lipid envelope