Introduction to viruses: Difference between revisions

Revision as of 15:50, 7 December 2008

Revision as of 09:42, 16 December 2008

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VII: [[dsDNA-RT virus]]es

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A '''virus''' is a usually-[[microorganismpathogenic]] (not all of them cause disease) chemical substance that [[reproduction|reproduces]] inside the [[Cell (biology)|cells]] of living hosts. When infected by a virus, a host cell is forced to produce many thousands of identical copies of the original virus, at an extraordinary rate. Unlike most living things, viruses do not have cells that divide; new viruses are assembled in the infected host cell. Over 2,000 species of viruses have been discovered.

[[Viruses]] are commonly (and erroneously) though to be [[Life#Definitions|living]] [[microorganisms]]. However, viruses are not considered to be [[Life#Definitions|alive]] because they don't metabolize, are not composed of cells, and nor do they maintain homeostasis.

A virus consists of two or three parts: all viruses have [[gene]]s made from either [[DNA]] or [[RNA]], long [[molecule]]s that carry the genetic information; all have a [[protein]] coat that protects these genes; and some have an [[viral envelope|envelope]] of fat that surrounds them when they are not within a cell. Viruses vary in shape from the simple [[tobacco mosaic virus|helical]] and [[icosahedron|icosahedral]] to more [[bacteriophage|complex]] structures. Viruses are about 100 times smaller than [[bacteria]], and it would take 30,000 to 750,000 of them, side by side, to stretch to {{convert|1|cm}}.