Lecture 14 - Virus Overview Flashcards
Name the four genomes of viruses
dsDNA
dsRNA
ssDNA
ssRNA
The protein capsids have what two shapes
icosahedral
helical
Cells release viruses be what two processes?
- Budding process where each virus leaves in a membrane bubble that stays around the virus capsid (called an envelope). Envelope has spikes embedded
- Lysis - viruses trigger cells to break open and release “naked” nucleocapsids. Spike proteins integrated directly into the capsid
*Viral infections may cause one of what five cellular outcomes
- Abortive (no progeny viruses produced)
- Lytic (acute process released by death of cell)
- Chronic, Non-Lytic (infected cells slowly release viral progeny without cell death)
- Latent (virus genome become integrated into cell DNA. It is dormant but may re-awake at anytime producing progeny)
- Transformation (virus causes cell to proliferate uncontrollably)
What is a capsid
A protein shell that may be icosahedral or helical in shape. It encloses the genetic material
What is the difference between + and - strands of genetic material
+ is same orientation as mRNA
- is the anti-sense orientation
What are the spike proteins?
They are on the extreme outside of both enveloped and non-enveloped viruses. They determine what cells the viruses can infect. Spike mutations are important for expanding the range of potential hosts a virus might infect.
What are the four basic morphologies of viruses
- Non-enveloped, naked icosahedral
- Enveloped icosahedral
- Non-enveloped, naked helical
- Enveloped helical
What are the two keys for the virus to replicate and cause disease within a cell
- Viruses must cause the replication of their genetic material
- Viruses must produce positive-stranded mRNA (+RNA) to replicate their protein components
Quickly state the 6 steps of virus replication
- Attachment via spike proteins on target cell
- Penetrate into cell by endocytosis or cell membrane fusion
- Virus uncoats protein capsid inside cell
- Viral genome is exposed and replication of viral protein structures and genome occurs
- New viral particles begin to assemble
- Complete virus particles are released from cell through budding or cell lysis
Naked, non-enveloped viruses are usually released how from the cell?
Cell lysis
Most viral infections follow what type of growth curve?
Simple one-step growth curve
On the growth curve, define eclipse period and growth period.
Eclipse period: period of time during which the virus uncoats and begins replicating its individual constituents
Growth period: Constituents are assembled into many complete viral particles, the total number of which equal the yield
All viruses need to be able to synthesize what type of mRNA to effectively carryout their replication in a cell and why?
Positive-strand (+) mRNA
-Viruses ‘hijack’ a cell’s normal mechanisms for translation of (+) mRNA into proteins.
Define Viremia
Release of viral agent into the blood
