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40 Cards in this Set

  • Front
  • Back
What are typical virus sizes?
30-200 nm
Shapes of viruses (3)
1. helical capsid
2. icosahedral capsid
3. viral specific proteins
5 Properties of viruses
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.
The definition of virion is
the extracellular state of a virus.
Humans warts is an example of which type of viral shape?
icosahedral symmetry (20 regular faces)
The tobacco mosaic virus is an
RNA virus which is helical.
How is the flu virus shaped?
it is enveloped
Lambda viruses are
bacteriophages, they are "bacteria eaters"
The viral genome contains
all the hereditary material of a virus, 4-200 genes.

dsDNA, ssDNA, dsRNA, ssRNA
A virus capsid is
a protein shell that surrounds the genome
what is the virus capsid used for?
-protecting the viral genome
-often needed for attachment to the host cell
A viral envelope is
the outer most later of the enveloped viruses which is composed of host lipids and viral proteins, it is often used for attatchment.
what is a packaged protein?
a protein that is found within the capsid. they are different for different viruses.
What is reverse transcriptase?
it is an enzyme that synthesizes DNA from an RNA template
What is RNA dependent RNA polymerase?
it is an enzyme that synhtesizes RNA from an RNA template.
Seven steps in phage attatchement.
1. attachement
2. penetration
3. expression of viral genes
4. genome replication
5. capsid formation
6. packaging
7. release
Attatchment of a phage is
the binding of a capsid or envelope protein to a host receptor (usually a specific protein, lipid, or polysachharide).
What determines the virus host range?
the specificity for host receptor
What is Viral penetration?
the injection of viral nucleic acid and packaged proteins.
When is a viral gene expressed?
once it replicates inside of the host via the host's machienery
What are some typical viral proteins?
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
What are various methods of genome replication?
via host enzymes only, viral enzymes only or host and viral enzymes
Capsid protein formation occurs via
self assembly
Packaging of a virus is?
the insertion of the nucleic acid into the capsid
what is a common packaging method?
the "headfull" method
How is a virus release from the host cell?
via lysis or budding
What are the 3 steps in lysogenic phage?
1. lysis
2. lysogeny
3. prophage induction
what is the most frequent method of reproduction?
What is lysogeny?
prophage integration. a virus integrates itself into the host genome
A lysogen is?
a cell with an integrated virus
How is a prophage replicated?
when the host replicates
what is prophage induction?
excision of the prophage followed by lytic replication.
what causes prophage induction?
UV light and other DNA damaging agents
How is a virus uptaken by an animal cell?
first attatchemtn and penetration occur, then the cell uptakes the virus via endocytosis
Do viruses need to adapt for eukaryotic cells?
yes, they need to follow eukaryotic rules like eukaryotic RNA processing compartmentation
Virus/ Host interactions.
1. lysis
2. persistent infection
3. latent infection
4. transformation
Lysis is
the destruction of the host cell.
Persistent infection is
viruses budding from host over a long period of time
Laten infection are
infections that reoccur periodically
Transformation is
the increased growth rate of host cells