Lecture 30 - Lecture 30: Nobel Price Chapter 19: Viruses...

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Lecture 30: Nobel Price Chapter 19: Viruses 19.1 A Virus Consists of a Nucleic Acid Surrounded by a Protein Coat The Discovery of Viruses: Scientific Inquiry -Adolf Mayer discovered he could transmit tobacco mosaic disease from plant to plant by rubbing sap extracted from diseased leaves onto healthy plants…suggested disease was caused by small bacteria invisible by microscope -hypothesis tested by Dimitri Ivanowsky who passed infected sap through filter and after filtration, sap still produced disease -Martinus Beijerinck proved that the infectious agent could reproduce only within the host -Wendell Stanley crystallized infectious particle Structure of Viruses -tiniest viruses: 20 nm -viruses are infectious particles consisting of nucleic acid enclosed in a protein coat, and in some cases a membranous envelope Viral Genomes -many viruses have genomes consisting of double stranded DNA, single stranded DNA, double stranded RNA, or single stranded RNA (virus is called DNA virus or RNA virus according to kind of nucleic acid) -genome usually organized as a single linear or circular molecule of nucleic acid…genomes of some viruses consist of multiple molecules of nucleic acid Capsids and Envelopes - capsid : protein shell enclosing viral genome -capsid may be rod-shaped, polyhedral, or more complex in shape -capsids built from capsomers , protein subunits … but the number of different kinds of proteins in a capsid is small -rod shaped viruses are called helical viruses ( tobacco mosaic cirus) -polyhedral capsid referred to as icosahedral viruses : adenovirus - viral envelope : derived from membrane of host cell contain host cell phospholipids and membrane proteins…and contain proteins and glycoproteins of viral origin (influenza: viral envelope) - bacteriophage ( phage ): viruses that infect bacteria
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Lecture 30 - Lecture 30: Nobel Price Chapter 19: Viruses...

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