Viruses lecture 2 Flashcards
Are ribosomes a feature of viruses?
no
Describe positive-strand RNA virus genomes
- simple open reading frame
- cassette their proteins into structural and non-structural
- 5’UTR and 3’UR
- sometimes Cap
- sometimes Poly(A)
- 1 start
- 1 stop
Which direction do negative strand RNA viruses get read?
right to left
What do negative strand RNA proteins do first when they invade a cell?
begin by replicating (must contain a polyerase in its capsid)
What are the four types of negative-strand RNA genomes?
- simple
- multiparte, simple
- multiparte, simple, ambisense
- multiparte, complex, ambisense
What does ambisense mean?
some bits of RNA translate n both directions
What is a mononegavirale?
single-stranded, single pieces of anti-sense viral RNA (must have a RNA polymerase as cells don’t have one)
Can viruses make a two codon translation?
yes
What does para mean?
correct/normal
What does ortho mean?
similar
Meta?
following after
Name the segmented viruses (BOARing)
bunyavirus, orthomyxovirus, arenavirus and reovirus
What makes it possible for reassortment of genetic information?
segmented genomes
What does reassortment achieve?
rapid generation of genetic diversity
What must all viruses contain at some point in their life cycle?
double stranded RNA as they have to replicate
What triggers an innate response?
the replication intermediate double stranded rNA which is normally never seen
In retroviruses where is the nucleocapsid protein found?
on the left, near 5’ end
Where is the envelop protein in retroviruses?
right
Where is the polymerase in retroviruses?
middle
How do retroviruses replicate?
make DNA from RNA and then RNA from the DNA that has been made
Are retroviruses nuclear?
yes always because they are DNA viruses half of the time
Why do viruses spread so quickly?
once a cell is infected it defends the virus inside it to avoid superinfection. It pushes the other virus away causing other cells to become infected (this occurs via A33 and A36 proteins)
What does VEHCS stand for?
Virally Encoded Host Cell Shutoff
How does polio produce viral proteins?
- Removes the cap binding complex on mRNA so that translation can’t occur
- Polio can bind directly to the ribosome using the internal ribosome entry site so it can produce proteins
How does HSV work?
to remain hidden it stays silent
-turns off everything other than a series of micro RNAs that control the host cell (not antigens) (immosilent and invisible)
What makes a virus more likely to spread?
by keeping host cells alive (more chance for transmission than if host cells are dying) (need to be less virulent)
What is the role of the HERV-W virus?
mediates the cell-cell fusion which forms the synciotrophoblast forming the fetal-parent barrier
Do all viruses contain RdR polymerases?
no HIV has a RdD polymerase (RNA dependent DNA polymerase)
