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VIRUSESCHAPTER 13

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What are Viruses?

Obligate intracellular parasites

Viral components– Nucleic acids

– Capsid

– Envelope

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Viral Shapes and Sizes Helical Spherical Polyhedral

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Infectious Properties

Viral Host range– Spectrum of host

Viral specificity– Types of cells

Viral Origins– Unknown

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Nucleic Acid

DNA viruses– ds DNA– ss DNA

RNA viruses– + strand– – strand– Double strand

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11 RNA Virus FamiliesPicornaviridae

Togaviridae Flaviviridae Retroviridae Paramyxoviridae Rhabdoviridae Orthomyxoviridae

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RNA Virus Families (cont.)

Filoviridae Bunyaviridae Arenaviridae Reoviridae

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DNA Virus Families Adenoviridae Herpesviridae Poxviridae Papovaviridae Hepadnaviridae Parvoviridae

Emerging Viruses: Previously endemic

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Viral Replication Activities

– Adsorption

– Penetration (virus or chromosome)

– Synthesis

– Maturation

– Release

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Bacteriophages

Plaque counts

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Culturing Animal Viruses Eggs Cell Culture

– Primary– Continuous

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Viral Cytopathic Effects Cytopathy

Teratogenic effects

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Viruslike Agents Satellites Prions Viroids

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