Virology: Virus Structure, Replication, Assays, and Host Interactions

58 flashcards

What is the typical size range for viruses?: Most viruses are about 20-300 nm.
Which virus has been used to control rabbit populations?: Myxoma virus.
What important biological process was first discovered in viruses?: Reverse transcription was discovered in retroviruses.
What technique is best for imaging enveloped virus particles?: Electron microscopy using negative staining or cryo-EM.
What technique is best for creating 3D models of virus particles?: Cryo-electron microscopy and image reconstruction.
What technique separates viral proteins by mass?: SDS-PAGE gel electrophoresis.
What technique separates viral nucleic acids?: Gel electrophoresis.
What technique measures infectious virus particles?: Plaque assay measured in PFU/mL.
What technique studies protein-protein interactions?: Co-immunoprecipitation.
What technique locates viral proteins inside infected cells?: Immunofluorescence microscopy.
What technique analyzes viral gene function?: Mutagenesis or reverse genetics.
What does a viral protein with a strong positive charge likely bind to?: Negatively charged viral DNA or RNA.
What is the likely function of a viral protein with a myristylation site?: Attachment to lipid membranes.
Which enveloped virus is bullet-shaped?: Rabies virus.
Which enveloped virus is rod-shaped?: Baculovirus.
Which enveloped virus is thread-shaped?: Ebola virus.
Which virus has an internal membrane?: Iridoviruses or Paramecium bursaria Chlorella virus 1.
Do most DNA virus capsid proteins have nuclear export signals?: No. Nuclear localization signals help proteins enter the nucleus.
How many faces does an icosahedron have?: 20 triangular faces.
Among which hosts are enveloped viruses rarest?: Prokaryotes such as bacteria and archaea.
What genetic material must every virion contain?: A viral genome made of DNA or RNA.
How can plant viruses enter their hosts?: Through insect vectors or other vectors and through wounds or grafting.
Which viruses are commonly transported by migrating birds?: Avian influenza viruses.
Why do many insect vectors experience little harm from viruses?: Some viruses may have evolved in invertebrates before spreading to vertebrates or plants.
What determines whether a host cell is susceptible and permissive to infection?: Suitable receptors and the cellular conditions needed for viral replication.
Which viruses commonly form protective occlusion bodies?: Baculoviruses.
Do all viruses evolve toward decreased virulence?: No. Virulence can increase or decrease depending on selection pressures.
What receptor does influenza virus bind to?: Sialic acid on host cell surface molecules.
What receptor does HIV-1 bind to?: CD4 with CCR5 or CXCR4 as a co-receptor.
What protein forms coated pits during viral endocytosis?: Clathrin.
What cell structure is used for dynein-mediated transport toward the nucleus?: Microtubules.
What best describes baculovirus entry and intracellular transport?: Baculoviruses enter cells and use host microtubules and actin-based transport to move within cells.
What is the AATAAA sequence associated with?: Polyadenylation signal for adding a poly-A tail to mRNA.
Do most viruses use the host cell translation machinery?: Yes. Viruses depend on host ribosomes to make proteins.
Which viruses are least likely to require RNA splicing?: Viruses that replicate entirely in the cytoplasm such as many RNA viruses.
What is the TATA sequence associated with?: Promoter region involved in starting transcription.
What additional polymerase activity does reverse transcriptase have?: DNA-dependent DNA polymerase activity.
Why is there one Baltimore class for ssDNA but two for ssRNA?: ssRNA can be positive-sense or negative-sense while ssDNA is grouped into one Baltimore class.
Where do most DNA viruses replicate?: In the nucleus with exceptions such as poxviruses.
Where do most RNA viruses replicate?: In the cytoplasm with exceptions such as influenza and retroviruses.
Where do retroviruses convert RNA into DNA?: In the cytoplasm.
Where do retroviruses produce RNA from DNA?: In the nucleus.
What type of primer is generally used for DNA replication?: An RNA primer or in some viruses a protein primer.
Do RNA viruses always require a primer for genome replication?: No. Many RNA-dependent RNA polymerases can initiate without a primer.
What enzyme replicates RNA virus genomes?: RNA-dependent RNA polymerase.
What enzyme copies retroviral RNA into DNA?: Reverse transcriptase.
Where do positive-sense and negative-sense RNA viruses have polymerase recognition signals?: At the appropriate ends of their RNA templates.
What type of DNA replication is used by adenoviruses?: Strand displacement replication.
What is viral self-assembly?: Viral proteins and genomes spontaneously form virus particles.
Why do complex viruses require directed assembly?: They need additional viral or host factors to assemble correctly.
How do many enveloped viruses leave cells?: By budding through a host cell membrane.
What viral proteins help budding occur?: Envelope proteins and matrix or capsid proteins interact during budding.
Why is tightly packaging viral nucleic acid difficult?: Negatively charged phosphate groups repel one another.
What cellular compartments are topologically equivalent to the outside of a cell?: The inside of membrane-bound compartments such as the ER and Golgi lumen.
How else can viruses leave cells besides budding?: Cell lysis or exocytosis.
What is a latent viral infection?: The viral genome remains in cells with little or no production of new viruses.
What is tetherin?: A host protein that prevents enveloped viruses from being released by budding.
What can happen when antibodies bind to a virion?: They may neutralize the virus and prevent infection.