Lecture #30 - Lecture 30 Animal Viruses Reading: Chapter...

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Lecture 30 Animal Viruses Reading: Chapter 9.1 – 9.7, 9.12 – 9.13, 16.8 – 16.9, 16.15, 26.7, 26.14, Viruses Viruses must complete life cycle within a “host” cell. Metabolically inert when outside a host cell. Viruses are “Polyphyletic” i.e., no obvious single evolutionary history.
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Classification of Viruses. • “Filamentous” vs. “icosohedral”. Filamentous Icosohedral • “Naked” vs. “enveloped”. • Can contain DNA or RNA. • Nucleic acid can be single-stranded or double-stranded. • If single-stranded, can be “+ stranded” (same orientation as the mRNA) or “- stranded” (opposite that of the mRNA). mRNA 5' . .. GAC UCG AGC . .. 3' “positive strand DNA virus” 5' . .. GAC TCG AGC . .. 3' “negative strand DNA virus” 3' . .. CTG AGC TCG . .. 5' “positive strand RNA virus” 5' . .. GAC UCG AGC . .. 3' “negative strand RNA virus” 3' . .. CUG AGC UCG . .. 5'
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A “cytolytic virus” kills the cells it infects, causing a plaque. A “transforming virus” causes cancerous proliferation of infected cells. Enveloped viruses generally infect host cells by membrane fusion, and lose their lipid envelope upon infection. Naked viruses generally infect by endocytosis, gaining a lipid envelope upon infection that they later lyse
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Poliovirus A “picornavirus” Positive-strand RNA virus. Spread by oral-fecal route. Colonizes gut without symptoms. Occasional escape to nervous system. Naked (i.e. no lipid envelope), single
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Lecture #30 - Lecture 30 Animal Viruses Reading: Chapter...

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