Virus Structure and Function Flashcards
Virion
Do they undergo division?
infectious, mature viral particle
• Do not grow or undergo division
- replicates using host machinery
Describe two means of classifying viruses.
The Classical System
The Baltimore System
The Classical System
Grouping by shared physical properties
- Nature of the genetic material (is it DNA or RNA?)
- Symmetry of the capsid (is it helical or icosahedral?)
- Naked or enveloped
- Dimensions of the virion and capsid
The Baltimore System
Based upon how they produce mRNA (The Central Dogma)
+ mRNA is the ribosome ready component
What type of genome is always in icosahedral capsids?
Q
Genome is always RNA
Do viruses with Helical or Icosahedral capsids have envelopes?
Almost all helical-packaged capsules in animal viruses have envelopes
Where on the virus are glycoproteins found?
viral glycoproteins embedded in the envelope membrane
there are proteins on the capsid as well
Which virus replicate in the cytoplasm? How?
Poxvirus (a dsDNA) - brings its own RNA pol to the party
Two periods/phases of viral replication cycle
Eclipse period
Latent period
What do viruses attach to when trying to infect? Which is more specific?
On the host membrane
- Protein receptors or
- Carbohydrate receptors (less specific)
• Virus will attach to anything it can attach to - no strict “rules” of which virus attaches to which receptor
- the receptor dictates the susceptibility or resistance of the cell
What is significant about entry of a virus? Why is this important?
• This is an energy-dependent process
Body will adapt when infected:
- shunt energy towards defense
- be less metabolically active
Does endosome formation with a virus apply to ones with or without envelopes?
Both can form endosomes
*but viruses with envelopes can fuse instead of forming an envelope
How are the goals of viral gene expression different from genome replication?
gene expression: goal is to make proteins
genome replication: goal is to replicate viral genetic material (many diff ways)
How is assembly of iscosahedral capsids diff than helical nucleocapsids?
Q
For icosahedral capsids packaging of the genome in one of 2 ways:
○ Capsid assembles around the virus genome or
○ Genome is “fed” into preformed capsids
For helical nucleocapsids viral genome is coated with nucleocapsid protein DURING synthesis of the genome
Diff types of Egress
- “Naked” capsids are released from cells by lysis
* Enveloped capsids egress by budding
