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22 Cards in this Set
- Front
- Back
Viruses
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Acellular
Viruses contain DNA or RNA Surrounded by a protein coat (capsid) Some are enclosed by an envelope with spikes Most viruses infect only specific types of cells in one host Host range is determined by specific host attachment sites and cellular factors |
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Virus Size
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Virus Structure
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Nucleic acid (genetic information)
DNA or RNA Capsid Protein subunits (protomers or capsomeres) Nucleocapsid : capsid plus nucleic acid Envelope (peplos) with spikes (peplomeres) |
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Helical viruses
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rod shaped
capsomers arranged in a helix |
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Complex viruses
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both helical and polyhedral components
bacteriophages |
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poxviruses
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Unknown symmetry
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Growing Bacterial Viruses
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Viruses must be grown in living cells
Bacteriophages infect bacterial cells and form plaques on a lawn of bacteria. |
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Bacteriophage T4
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first discovered and most studied bacteriophage
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Multiplication of Bacteriophages (Lytic Cycle)
Steps 1-3 |
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Multiplication of Bacteriophages
Steps 4-5 |
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One-step Growth Curve
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Taxonomy
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Viruses are grouped into families based on similar physical properties
EX: DNA or RNA capsid morphology enveloped or naked ds or ss nucleic acid if ss RNA is it + or – if ds DNA id it circular or linear Family names end in -viridae |
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Growing Animal Viruses
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Viruses must be grown in living cells
live animals enbryonated eggs tissue culture (eucaryotic cells) |
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Tissue Culture
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Animal viruses may also be grown in cell culture.
Normal cells or primary cells are grown in monolayers on plastic Transformed or continuous cell cultures form foci |
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Multiplication of Animal viruses
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Penetration and Uncoating by fusion
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Penetration and uncoating by fusion
simultaneous in time Entire Nucleocapsid enters cell |
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Penetration and Uncoating by endocytosis
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Penetration by endocytosis
Entire nucleocapsid enters cell |
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Multiplication of a DNA –Containing Animal Virus
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RNA-Containing Viruses
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RNA viruses must code for RNA Dependent RNA Polymerase
no RDRP present in cells RNA —> RNA |
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Multiplication of a Retrovirus
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Retroviruses
RNA viruses that can make DNA RNA —> DNA Require reverse transcriptase (RDDP) RNA dependent DNA polymerase |
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Retrovirus Phase I (integration)
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Phase I (integration) is under control of the virus
viral RDDP converts vRNA to vDNA viral integrase inserts vDNA into cell chromosome |
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Retrovirus Phase II (multiplication)
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Phase II (multiplication) is under control of the cell
cell DDRP transcribes viral message from provirus cell ribosomes translates viral message into viral proteins virus assembles and buds from cell |