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36 Cards in this Set
- Front
- Back
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Size of a Virus |
20-500nm in diameter; 100x smaller than bacteria |
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Tobacco Mosaic disease |
1800s first discovered virus- Adolf meyer killed virus with heating (80) dimitri ivanofsky 1892- tried bacteria filter Martinus Beijerinick 1898- termed virus; filtered sap still caused disease |
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Twort and d'Herelle |
1st description of bacteriophages in 1915 and 1917 formation of plaques |
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Phage therapy |
bacteriophage poured on wounds faded after antibiotics |
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Regressive hypothesis |
viruses may have once been small cells that parasitized larger cells; genes not needed for parasitism were lost |
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Cellular origin hypothesis |
viruses may have evolved from bits of DNA or RNA that "escaped" from the genes of a larger organism ie plasmids or transposons (jumpong genes) |
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Coevolution hypothesis |
viruses may have evolved from complex molecules of protein and nucleic acid at the same time as cells first appeared on earth and have been dependent on cellular life for billions of years - viroids and prions |
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Panspermia hypothesis |
viruses and other microorganisms are raining down from outer space upon the Earth |
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Impact of viruses: understanding of biology |
identification of promoters for eukaryotic rna polymerases understanding of enzymes involved in dna replication isolation and characterization of cellular oncogenes |
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Edward Jenner |
cowpox vaccine 1796 |
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Poliomyletitis |
ancient egypt and outbreaks in us |
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Smallpox |
300-500 million in 20th century spanish conquest was aided by smallpox epidemics, native americans |
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Foot and mouth disease |
threatened cattle since 6th century |
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SARS |
2002-2003 flu in china mobilization of global health labs and use of modern technology to track cases and identify viral agent |
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Influenza |
1918 spanish flu pandemic 20-50million people H1N1 H5N1 |
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Primary cell line |
cells taken right from the organism; limited lifespan |
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Host cell constraints |
host cell must express specific proteins that virus needs to infect and replicates within the cell eukayotes only translate monocistronic RNA viral mRna have competition for cell machinery dna polymerase enzymes not available in differntiated cell |
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Susceptible cell |
has the appropriate receptor allowing the virus to enter the cell. cell may or may not be able to support viral replication |
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Resistant cell |
lacks the appropriate receptor allowing the viris to enter the cell |
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Permissive Cell |
has the capacity to replicate virus |
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non-permissive cell |
cannot support or prohibits replication of a particular virus abortive or nonproductive infection |
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Central Dogma |
DNA--> RNA--> Proteins |
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Monocristonic RNAs |
eukayotic machinery only translates this; one RNA one message, only codes for one protein |
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How viruses exploit monocristonic machinery |
viruses contain separate mRNAs for each protein ; some have multiple genes on a single RNA molecule that is translated into single molecule with three cleavable protiens |
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How viruses deal with competition for machinery (mRNA suppession) |
viral nuclease decapitates host mRNA, capless host cell mRNA are degraded by cellular exoribonucleases; viral capless MRNA are spared |
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Virus Translational Shutoff |
virus can evolve ways to inhibit different components of of the multi-subunit translation initiation complex |
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Viruses can only infect undifferentiated cells with active DNA polymerase |
can push differentiated cell into the cell cycle |
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Viral structure |
nucleic acid DNA or RNA outer shell (capsid) -nucleocapsid: nucleic acis genome packaged within the capsid +/- envelope |
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Functions of the viral capsid |
protects from: physical, chemical, and enzymatic damage. Virus need protection until it fins a suseptible and a permisive cell |
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Capsid design problem |
genome can only code for a protein that is 15%of its weight therefore capsids are made of identical protein subunits helical symmetry cubic/ iscosahedral |
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Structure units of viral capsid |
the smallest functional equivalent building units of the capsid (the single protein) |
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Viral Capsomers |
morphological units seen on the surface of particles and represent clusters of structure |
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Viral capsid |
denotes the protien shell that encloses the nucleic acid |
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Nucleocapsid |
refers to capsid together with its enclosed nucleic acid |
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Self assembly of the virus |
polar heads on the outside and nonpolar tails on the inside. will assmeble and dissasemble until most stable stucture is formed, sometimes capsid formed without genome inside, not infectious but immuno genic |
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Helical capsids |
simplest way to arrange multiple identical protein subunits in rotational symmetry witha central cavity; length of capsid related of nucleic acid |
