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6 Cards in this Set
- Front
- Back
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How do Koch's postulates differ for viruses?
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The agent must be present in every case of the disease.
The agent must be isolated from the host (NOT & grown in vitro.) The disease must be reproduced when a pure culture of the agent is inoculated into a healthy susceptible host. The same agent must be recovered once again from the experimentally infected host. NEW: The agent must be able to passage through ceramic filters that could retain the smallest bacteria |
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What is the genomic make-up of viruses? Capsid or no? Envelope or no?
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Small: 20 to 300 nm
Genome: either DNA or RNA (dsDNA, ssDNA, ssRNA, dsRNA) Capsid Some have envelopes Live cell as host Infectious |
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What is the genomic make-up of viroids? Capsid or no? Envelope or no?
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Very small,
Genome: circular RNA molecules, RNA has a rod-like secondary structure it does not encode any protein no capsid or envelope which are associated with certain plant diseases. Replicate like a virus obligate intracellular parasites. |
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What is the genomic make-up of virusoids? Capsid or no? Envelope or no?
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They are also called Satellites.
Very small, single-stranded RNA molecules that lack genes required for their replication. Encode one or two structural proteins. Replication are dependent on the presence of plant virus replication (hence 'satellite'). Virusoids, while being studied in virology, are not considered as viruses but as subviral particles. Since they depend on helper viruses, they are classified as satellites. |
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What is the genomic make-up of prions? Capsid or no? Envelope or no?
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Infectious protein
No nucleic acid a single type of protein molecule with no nucleic acid component. The prion protein & the gene which encodes it are also found in normal 'uninfected' cells. Brain diseases: Creutzfeldt-Jakob disease in humans, scrapie in sheep bovine spongiform encephalopathy (BSE) in cattle. |
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What are the three theories of viral evolution?
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Regressive
Cellular components that learned to live alone Independent existence evolved in parallel to RNA world. |
