Virology 1 & 2 Lecture - Ryan Flashcards
Can viruses generate their own energy?
no, they must use what host cells produce
Compare the size of viruses to bacteria?
viruses are much smaller. the smallest bacteria are just barely of a comparable size to the largest viruses
What is a viroid?
infectious nucleic acid but has no protein component. Fairly limited to plants.
What is a prion?
infectious proteins with no nucleic acids with them
What type of RNA is the same sense as the messenger RNA?
+RNA
What type of virus can have segmented genomes (chromosome like)?
only RNA viruses. DNA viruses are always one unit, either single or double stranded
Which type of polymerases have proof-reading function?
only DNA polymerases. RNA polymerases do not and tend to make a lot of mistakes. This limits the size of RNA viruses
What is concerted assembly?
as the nucleic acid is assembled, capsid proteins self-assemble around it at the same time. Common for helical structures
What is sequential assembly headful packaging?
capsid structure is assembled independently from genome replication. Common for icosohedrals
Why do viruses use repeating subunits?
efficiency so all the products can be encoded by the viruses small genome
What are the consequences of virus envelopes?
it is a layer of protection. It changes how it enters and leaves cells.
They make viruses less stable. Always found in liquid environments
What are the two ways viruses penetrate cells? Which one is pH dependent?
endocytosis - pH dependent
plasma membrane fusion - pH-independent
What does early transcription occur immediately before?
genome replication
Where do most DNA viruses replicate?
Nucleus
Where do most RNA viruses replicate?
cytoplasm
Virus A enters the cells by endocytosis, its naked genomes can be detected in the cytoplasm of infected cells, and virus A causes diarrhea. what can you tell about the structure?
non-enveloped RNA that is likely icosohedral because there are “naked genomes in the cytoplasm” suggesting sequential replication
Why do RNA viruses have to make their own RNA polymerase molecules?
Human host cells only have DNA polymerases, not RNA polymerases that would work for replication.
What is the key difference in packaging between +RNA and -RNA viruses?
-RNA viruses MUST package an RNA-dependent RNA polymerase with the -RNA otherwise it won’t be able to infect other cells.
What type of DNA will retroviruses produce: single or double stranded?
double stranded. This allows them to use host RNA polymerase II for transcribing viral genes
Which is more infectious: a virus with a high or low particle-pfu ratio?
lower particle-pfu ratios mean there are more infectious virions per physical particle so lower ratios are more infectious
What is complementation? Which type of viruses can this happen in?
sharing of viral proteins.
Happens in high frequency for both RNA and DNA viruses
You are provided a test tube mixed with two isolates of RNA virus and you are told the total titer. When you infect cells at an MOI of 0.1, no lysate is obtained. When you infect cells at n MOI of 10, a lysate is obtained. How can this be explained?
Most likely complementation. Could also be recombination but complementation is much more common.
What is a syncitium?
multinucleated cell formed from merging of a virally infected cell with a previously non-infected cell
What does PKR pathway respond to?
double stranded RNA
