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Unformatted text preview: Ch. 13- Viruses Virus- a cellular, not living, contain nucleic acid & protein component. Some viruses will infect a cell, they will hibernate. Post-pone replication some will enter a cell & reproduce very quickly. (30 minutes or more). A cellular- requires a host or living system to reproduce in. Tobacco mosaic virus- killing tobacco crops. Took plant, grinds it up, run it through a filter, filter very fine to remove all the bacteria. He had liquid filtrate, and then put it on another healthy plant, it caused the same disease. Repeated. Later 1898 another guy did the same thing, put it through an agar gel, he then saw the infectious agent affected crop called contagium vivum fluidium- shortened to virus. Later Stanley crystallized the virus, used electron microscopy- looked at structure- looked nothing like any life form- so they called it an infectious agent. They found it had a genetic core & put in a protein capside, now we know more. Classified as intracellular parasite, never arise directly from a pre-existing virus. Will require a host of some type, prokaryotic or eukaryotic. Uses the hosts synthetic machinery to replicate itself and destroy the host. Does not have cell walls or ribosomes, so anti-biotic will not affect. 4 main traits to describe a Virus: Genome- DNA or RNA Single or double stranded Simple or complex shape Membrane is surrounded by a capside or an envelope Reproductive Cycles: (both can affect but lysogenic generally doesnt): 1-...
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