Virology Flashcards
What type of genetic material do viruses contain?
Either DNA or RNA
Never both!
Why do viruses require a host cell for replication?
Because they lack their own, independent metabolic machinery
The virion is the ? life cycle, while the virus is the ? life cycle.
Virion = Structural form, extracellular (infectious form, outside host cell, cannot replicate)
Virus = Non-structural form, intracellular (nuceloprotein form, inside host cell, can replicate)
What type of viral pathogens affect plants?
Subviral particles like viroids (replicate in nucleus) and virusoids (replicate in cytoplasm), both of which lack protein coating (capsid) of viruses.
What causes a prion to produce disease?
Any conformational aberration of the normal cellular prion protein (PrPc –> PrPsc)
What are prions?
A small protein capable of producing neurodegenerative disease. Have long incubation periods and do not produce immune/inflammatory responses in host.
Prions are NOT viruses!
What type of virus is more resistant to inactivation, and how does this serve as advantage?
Non-enveloped because they lack the envelope that coats/surrounds the nuceloprotein; these viruses can cause year-long diseases
The lipid molecules of enveloped viruses are very labile, and thus are more easily inactivated
Where are antigens located on enveloped viruses?
On the spike/peplomer glycoproteins
A spike protein or peplomer protein is a protein that forms a large structure known as a spike or peplomer projecting from the surface of an enveloped virus
Acute infections and lysogenic cycles are associated with what type of virus?
Non-enveloped
Budding is a non-lytic and non-lethal mechanism of pathogenesis associated with what type of virus?
Budding thus allows for long-term coexistence b/w host & virus –> chronic, persistant infections
Enveloped viruses
What are the two ways that viruses’ nucleoprotein can be organized?
1.Helical
2. Cubical (icosahedral) symmetry
Which nucleocapsid symmetry features efficient packaging of the viral genome?
Icosahedral (cubical)
What are the 3 major differences between DNA and RNA viruses?
- DNA genome = ds or circular; RNA genome = ss or segmented
- DNA nucleocapsid = icosahedral; RNA nucleocapsid = icosahedral or helical
- DNA is typically larger (kb) than RNA
What is the function of the viral attachment protein (VAP) on a virion?
Serves as a ligand that binds to the host cell’s glycoprotein receptor, initiating infection
Where is the VAP located on a non-enveloped versus enveloped virion?
Non-enveloped: a part of the surface proteins that form the external structure of the nucleocapsid
Enveloped: one of the surface proteins that form the spikes protruding out from the viral envelope
Polymerase in viruses performs what?
Transcribing dsDNA or dsRNA into mRNA
Reverse transcriptase in retroviruses performs what?
Transcribing RNA into DNA
Retrovirsues can become proviruses once transcribed into DNA, by beinig inserted into the host genome by integrase
Hemagglutinin helps spread the influenza (enveloped) virus cell-to-cell and initiate infection, and the SARS-CoV-2 vaccine targets the spike/peplomer glycoproteins of enveloped viruses. These are two examples of how these glycoproteins can serve as what?
- enzymes
- antigens
How do enveloped viruses develop their lipid bilayers?
through interactions with the host cell they infect
A disease that produces multiple, continuous transmissions in a define population/region/time is what kind?
Endemic (Enzootic)
Enzootic = non-human equivalent
A disease whose peaks in incidence exceed their endemic (enzootic) baseline is what kind?
Epidemic (epizootic)
Epizootic = non-human equivalent
“Number of cases in a population”
cases / population
Disease Rate
“Case:Population ratio”
where population defines both size of a population and a time frame
acute diseases of short duration
Disease Incidence or Attack Rate
“Case:Population ratio”
where population is solely defined by number of subjects
chronic diseases
Disease Prevalence
Incidence/Attack Rate = C/P = (S/P)(I/S)(C/I)
Interpret this equation.
- C/P = Case/Population
- S/P = Suspects/Population = the proportion of the population which is susceptible
- I/S = Infected/Population = the proportion of the population which is infected
- C/I = Cases Diseased/Cases Infected = the proprtion of those infected who are diseased
“The continued reportingof diseases”
Surveillance
What are the cons about serological survery?
Serological surveys detect antibody presence
- Data do not define the precise moment of infection
- Data do not distinguish b/w antibodies present due to natural infection vs. vaccination
What type of studies analyze events that are predicted to happen in the future?
Prospective studies