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40 Cards in this Set
- Front
- Back
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What are typical virus sizes?
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30-200 nm
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Shapes of viruses (3)
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1. helical capsid
2. icosahedral capsid 3. viral specific proteins |
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5 Properties of viruses
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1. small
2. non-cellular 3. replicate within host and take over host machienery 4. released from host cell to infect other cells 5. often damage or kill the host. |
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The definition of virion is
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the extracellular state of a virus.
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Humans warts is an example of which type of viral shape?
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icosahedral symmetry (20 regular faces)
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The tobacco mosaic virus is an
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RNA virus which is helical.
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How is the flu virus shaped?
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it is enveloped
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Lambda viruses are
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bacteriophages, they are "bacteria eaters"
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The viral genome contains
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all the hereditary material of a virus, 4-200 genes.
dsDNA, ssDNA, dsRNA, ssRNA |
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A virus capsid is
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a protein shell that surrounds the genome
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what is the virus capsid used for?
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-protecting the viral genome
-often needed for attachment to the host cell |
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A viral envelope is
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the outer most later of the enveloped viruses which is composed of host lipids and viral proteins, it is often used for attatchment.
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what is a packaged protein?
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a protein that is found within the capsid. they are different for different viruses.
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What is reverse transcriptase?
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it is an enzyme that synthesizes DNA from an RNA template
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What is RNA dependent RNA polymerase?
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it is an enzyme that synhtesizes RNA from an RNA template.
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Seven steps in phage attatchement.
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1. attachement
2. penetration 3. expression of viral genes 4. genome replication 5. capsid formation 6. packaging 7. release |
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Attatchment of a phage is
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the binding of a capsid or envelope protein to a host receptor (usually a specific protein, lipid, or polysachharide).
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What determines the virus host range?
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the specificity for host receptor
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What is Viral penetration?
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the injection of viral nucleic acid and packaged proteins.
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When is a viral gene expressed?
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once it replicates inside of the host via the host's machienery
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What are some typical viral proteins?
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1. capsid proteins
2. proteins that block gene expression 3. proteins that block restriction systems 4. proteins for genome replication 5. proteins for assembly of viral particles |
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What are various methods of genome replication?
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via host enzymes only, viral enzymes only or host and viral enzymes
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Capsid protein formation occurs via
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self assembly
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Packaging of a virus is?
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the insertion of the nucleic acid into the capsid
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what is a common packaging method?
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the "headfull" method
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How is a virus release from the host cell?
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via lysis or budding
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What are the 3 steps in lysogenic phage?
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1. lysis
2. lysogeny 3. prophage induction |
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what is the most frequent method of reproduction?
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lysis
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What is lysogeny?
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prophage integration. a virus integrates itself into the host genome
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A lysogen is?
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a cell with an integrated virus
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How is a prophage replicated?
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when the host replicates
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what is prophage induction?
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excision of the prophage followed by lytic replication.
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what causes prophage induction?
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UV light and other DNA damaging agents
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How is a virus uptaken by an animal cell?
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first attatchemtn and penetration occur, then the cell uptakes the virus via endocytosis
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Do viruses need to adapt for eukaryotic cells?
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yes, they need to follow eukaryotic rules like eukaryotic RNA processing compartmentation
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Virus/ Host interactions.
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1. lysis
2. persistent infection 3. latent infection 4. transformation |
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Lysis is
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the destruction of the host cell.
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Persistent infection is
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viruses budding from host over a long period of time
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Laten infection are
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infections that reoccur periodically
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Transformation is
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the increased growth rate of host cells
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