Viruses_and_Bacteria

Viruses_and_Bacteria - TheGeneticsofVirusesand Bacteria...

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    The Genetics of Viruses and  Bacteria
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Discovery of Viruses Tobacco mosaic virus (TMV) - stunts  leaf growth and leaves mosaic  coloration
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Discovery of Viruses Scientists were puzzled by cause of  TMV symptoms Could be passed through contact with  infected sap (Mayer 1883) Could not be stopped by bacterial filter  (Ivanowsky 1893) Passed infection to successive generations Could not be cultured and grown in lab,  needed host to reproduce
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Discovery of Viruses A structure smaller than bacteria was  expected 1935 - Wendell Stanley Crystallized virus Cells can’t crystallize Viruses are - infectuous particles  consisting of nucleic acid inside a protein  coat
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Relative Size of Viruses
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Viral Genomes DNA Viruses Double stranded DNA Single stranded DNA RNA Viruses Double stranded RNA Single stranded RNA CAN BE CIRCULAR!
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Viral Structure Protein shell encasing viral genome is  called a  capsid Many different shapes and sized Some viruses have  viral envelopes  -  membranous envelope - derived from  host cell membrane
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Arts and Crafts! Using the handout, please create your very  own Dengue Virus! With this miraculous specimen, you can Cause severe headache, muscle and joint pains  Give a bright red rash Occasionally cause gastritus – which is a  combination of nausea, diarrhea, and vomiting!
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Viral Reproduction Limited range of cells –  host range some are interspecies specific, others are  unique to species Interact with specific receptors on the  outside of cells (which receptor for  HIV?) Inject genetic information
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Viral Reproduction If genetic information is DNA Reprograms cell to copy viral DNA and  manufacture proteins (which proteins?) Use host DNA Polymerase If genetic information is RNA Use special virus encoded polymerases  that can use RNA as a template
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Viral Reproduction Newly minted genetic information and  capsid proteins self-assemble and leave  the infected cell Oftentimes this departure causes cell  lysis
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Phage Reproduction Reproduction by two alternative  methods: Lytic cycle  – cycle that ends with the  death of the host cell ( Virulent  Phage) Lysogenic cycle  – replicated phage  genome without destroying host cell  ( temperate  phages)
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Viruses_and_Bacteria - TheGeneticsofVirusesand Bacteria...

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