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Chapter 13a - Viruses Viroids and Prions • Virus(Latin...

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Unformatted text preview: Viruses, Viroids and Prions • Virus (Latin word for poison) – DNA or RNA not both – Protein coat – Infect only specific types of cells – host range • Determined by specific host attachment sites and cellular factors – Multiply inside host cell using host cell’s machinery – Cause synthesis of specialized structures to transfer viral particles to other cells • Virion is a complete, fully developed, infectious viral particle – Contains nucleic acid and a protein coat that protects and helps in transmission between hosts • Prions are infectious proteins Viruses Viral Classification • 3 primary means of classification • Nucleic acid – DNA or RNA (never both) – can be either single-stranded or double-stranded – can be linear or circular, some are even segmented • Morphology of protein coat (capsid) – protein subunits called capsomeres – Some have envelope – Some envelopes have spikes • Replication strategy Helical Viruses Polyhedral Viruses Complex Viruses • An infected host should produce antibodies to inactivate the virus – Some escape antibodies because regions of the genes that code for the viruses’ surface proteins are susceptible to mutations – can code for different “strains” of the virus that have altered surface proteins Viral Taxonomy • Family names end in –viridae – Classified by nucleic acid type, replication strategy and morphology • Genus names end in -virus • Viral species – A group of viruses sharing the same genetic information and ecological niche (host) – Common names are used for species – Subspecies are designated by a number Viral Taxonomy • Herpesviridae – family – Herpesvirus – genus • Human herpes virus 1, HHV 2, HHV 3 - species • Retroviridae – Lentivirus • Human Immunodeficiency Virus 1, HIV 2 Isolation and Cultivation of Viruses • Viruses must be grown in living cells – Bacteriophages form plaques on a lawn of bacteria • Animal viruses may be grown in living animals or in embryonated eggs •...
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Chapter 13a - Viruses Viroids and Prions • Virus(Latin...

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