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One of several possible viral classifications : * Class I double stranded DNA * Class II single stranded DNA * Class III double stranded RNA * Class IV positive single stranded RNA itself acting as mRNA. * Class V negative single stranded RNA used as a template for mRNA synthesis. * Class VI positive single stranded RNA with a DNA intermediate in replication but and in mRNA synthesis. |
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The protective coat normally also enables the infective process which can occur by a variety of different mechanisms. The practical upshot all off of these is that the host cells replication machinery is hijacked to create more of the virus particles hence completing the life cycle. Viruses are somewhere between being living and non-living. They can reproduce and show inheritance, but are reliant on the complex enzymes of their hosts, and in many ways can be treated like ordinary molecules (for instance, they can be crystalized). Whether or not they are "alive" it is clear that the are obligate parasites, and have no form which can reproduce independant of their host. Like most parasites they have a specific host range, sometimes specific to one species (or even limited cell types of one species!) and sometimes more general. |
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The protective coat normally also enables the infective process which can occur by a variety of different mechanisms. The practical upshot all off of these is that the host cells replication machinery is hijacked to create more of the virus particles hence completing the life cycle. Viruses are somewhere between being living and non-living. They can reproduce and show inheritance, but are reliant on the complex enzymes of their hosts, and in many ways can be treated like ordinary molecules (for instance, they can be crystalized). Whether or not they are "alive" it is clear that they are obligate parasites, and have no form which can reproduce independant of their host. Like most parasites they have a specific host range, sometimes specific to one species (or even limited cell types of one species!) and sometimes more general. |
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* Retroviruses |
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