Quiz 6 Flashcards
What are the names of two genera within the family Togaviridae?
Alphavirus
Rubivirus
What type of proteases carry out the site-specific cleavage of viral polyproteins that occurs in i) P-spaces ii) E-spaces?
P spaces: virus encoded enzymes
E Spaces: host encoded enzymes
Which of its co-translationally-cleaved polyprotein fragments encode poliovirus non-structural proteins?
P2, P3
What are the primary fates of poliovirus genomic (+)-ssRNA molecules i)at early times after initiation of the infection cycle; and, ii) at late times after initiation of the infection cycle?
Early-genome replication making (-)strand so they can then use the (-) strands to synthesize (+) strands
Late- Replication ends and then proceeds to assembly and maturation of the virion
Gene expression can happen early or late.
Briefly describe the events that occur during the initiation of poliovirus RNA synthesis.
P3 binds to 3’ end of viral RNA
3D RNA pol synthesized and attaches first 5’ nucleotide to Vpg
3D polymerase stalls after a few nucleotide bases because it is still tethered to P3
What normal, cellular processes are required for toga virus i) penetration, and ii) uncoating?
i) clathrin mediated endocytosis
ii) acidification of the endosome causing conformational changes in the virion
What two genetic mechanisms have contributed to the evolution of rubella virus and sindbis virus since their divergence from a common ancestor?
- Mutation
- Recombination
From what host species was influenza virus A/Shanghai/2/2013 (H7N9) isolated? is this strain associated with propagated epidemics in humans?
Humans, and no it wasn’t a propagated epidemic since it is H7N9.
Only H1-3 and N1and 2 can be transmitted to humans.
Which of the the Sindbis virus replication complexes can synthesize i) both 49s (+)-ssRNA and 26S (+)-ssRNA, and ii) both 49S (+)-ssRNA and 49S (-)-ssRNA
i) nsP1 + nsP2 + nsP3 + nsP4
ii) nsP1 + nsP23 + nsP4
What are the two different mechanisms that might be employed by non-enveloped viruses in order to penetrate a eukaryotic host cell?
Direct Injection
Endocytosis
From the perspective of the host, what are two positive effects that immune responses can have during a virus-host interaction?
- clearing of the virus
- Resolution of infection
What are the two main factors that determine the tissue tropism observed for a given virus?
- prescence of specific protein receptors on the host in the specific organ or tissue
- whether the virus can get into the specific tissue
What specific stage of the cellular infection cycle would you expect to be blocked by i) a/b interferons ii) neutralizing antibody?
i) Gene expression
ii) attachment
What is the normal generation time of a virus infection that occurs in a dead end host? Explain your reasoning.
There isn’t a generation time of a virus infection of a Dead end host since the pathogen can’t be transmitted. Therefore the generation time is infinite since the host is infected but does not transmit.
What two kinds of macromolecule do extracellular virus particles invariably contain?
nucleic acid
proteins
What are the two different kinds of virus-encoded proteins that may be involved in genome replication?
- modifier subunits
- Nucleic acid polymerase
In the NdNp notation, what is the designation of a reverse transcriptase activity?
RdRp
What is a cap structure? On what type of macromolecule would a cap structure be found?
Cap structure is a 7-methyl GTP that is attached 5’ to 5’.
The cap structure is found on a mRNA
The double helix is naturally occurring double-stranded nucleic acids is always antiparallel. What is an antiparallel double helix?
double helix strands that run parallel to each other with opposite alignments.
By what two mechanisms can genetic variability be introduced into any kind of virus
Mutation
Recombination
What are the two fundamental mechanisms by which viral nucleoproteins can be assembled?
Nucleation
Shell stuffing
To what taxonomic entity (i.e. order, family, subfamily, genus, or species) does each of the following belong?
(i) Herpesvirales
(ii) Orthomyxoviridae
- order
- family
What fundamental characteristic of all DNA polymerases allows some of them to carry out “proofreading” during DNA synthesis?
all DNA polymerases require a primer that helps facilitate the process of proofreading
Briefly explain the ‘copy choice’ mechanism that leads to recombination between sRNA viruses
RNA polymerase binds to the 3’ end of the template and synthesizes 5’ to 3’. During RNA synthesis the RNA polymerase may unattached from its template strand and go onto a new strand, carry nascent RNA strand with it. The newly synthesized strand will contain sequences from the original template as well as the new template strand. Depending on the attachment of the RNA polymerase to the new template depends on the newly synthesized strand will be homologous or non homologous.
