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14 Cards in this Set
- Front
- Back
What is a virus particle (Virion)?
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infectious form of virus that exists outside host and facilitate transmission from one host to another
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What is a virion composed of?
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Nucleic acid genome surrounded by protein coat and in some cases a lipid membrane layer
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What are characteristics of a viral genome?
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DNA/RNA
double or single stranded Mostly linear very specific Size range=0.02 to 0.3 um |
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What is a capsid?
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protein shell that surrounds the genome of a virus particle: Composed of capsomeres arranged in repetition around nucleic acid genome
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What is a capsomere
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Protein subunit of rapid
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Nucleocapsids are highly symmetric. What are types of symmetry?
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Helical symmetry: rod shaped virus (ex. tobacco mosaic virus)
Icosahedral symmetry: spherical viruses |
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What enzymes do virions contain?
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1) Lysozyme: lyse bacterial cell wall
2) Nucleic acid polymerases: For replication of viral genome, not dsDNA |
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What is a titer?
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Number of infections units per volume of fluid
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What is efficiency of plating?
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Number of plaque forming units always lower than microscope counts:
-inactive virions -mutant genomes -conditions not appropriate in lab for infectivity |
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Phases of viral replication?
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1) Attachment (adsorption)
2) Entry 3) Synthesis 4) Assembly 5) Release |
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What mechanisms do bacteria contain to diminish viral infection?
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1) CRISPR: similar to RNA interference
2)Restriction-modification system: effective against dsDNA virus, restriction enzymes cleave DNA, Modifies host own DNA to prevent cleavage of own DNA |
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Characteristics of early viral proteins?
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-synthesized soon after infection
-necessary for replication of virus nucleic acid -typically act catalytically -made in small amounts |
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Characteristics of late viral proteins?
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-synthsized later
-include proteins of virus coat -typically structural components -made in larger amounts |
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!Special modification in Phage T4 DNA?
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contains modified base: 5-hydrozymethylcytosine, DNA is resistant to most restriction enzymes!
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