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Virus

Scientific classification
Domain:Virus

Viruses can be classified in several ways, such as by their geometry, by whether they have envelopes, by the identity of the host organism they can infect, by mode of transmission, or by the type of disease they cause. The most useful classification is probably by the type of nucleic acid the virus contains and its mode of expression. This classification was proposed by Nobel-prize winner David Baltimore. It should be noted that none of these classifications are expected to be phylogenetic, as viruses may not share a common origin.

1 Overview

The various forms of viruses arise because one of the two strands of DNA in which all cellular life forms store their genetic information is redundant, so that viruses can have either single-stranded or double-stranded genomes. Furthermore, some viruses store their genome in RNA rather than in DNA form. RNA arises in cells as an intermediate when genes are translated into proteins. RNA genomes of viruses can be encoded in two different directions: Either the genes are stored in the 5'->3' direction (positive or + polarity), analogous to the direction in which genes are represented in mRNA in cells, or the genes are stored in the opposite direction (negative or - polarity).

The taxonomy of viruses is similar to that of all other forms of life:

Class (determined by genome type and mode of expression)
Order (...virales)
Family (...viridae)
Subfamily (...virinae)
Genus (...virus)
SpeciesThis article discusses biological species. Also see combinatorial species for the mathematical meaning of the term. Species is also a movie by Roger Donaldson. In English "species" is both singular and plural. The word " specie" is unrelated and is used t ( virus)

The division of classes into orders is very recent. To date, only 3 orders have been named, and many families have not yet been classified into orders. Approximately 80 families and 4000 species of virus are known.

2 Classification by genome type

2.1 DNA viruses

2.1.1 dsDNA viruses (double stranded DNA)



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Topics: Virus Classification, Overview, Classification By Genome Type...

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