Virus Families and Classification (MST1 L2-10) Flashcards
Which viral families are non-enveloped?
Reo, Calici, Picorna, Parvo, Papova, Adeno
Which family has ds RNA?
Reo
Which families have circular DNA?
Papova, Hepadna
Which families have a helical capsid?
Corona, Filo, Rhabdo, Bunya, Orthomyxo, Paramyxo
Do any of the DNA viruses have a helical capsid?
No
Which viruses with helical symmetry are non-enveloped?
None
What type of symmetry do all of the –ssRNA viruses have? Which families are these?
All helical.
Filo, Rhabdo, Bunya, Orthomyxo, Paramyxo
Which virus has a ds RNA genome? What kind of morphology does it have?
Reovirus. Non-enveloped, Icosahedral.
Which viruses have a +ssRNA genome? Do they all share the same morphology?
Calici, Picorna, Flavi, Toga, Retro, Corona.
No.
Calcici and Picorna are Icosahedral and non-enveloped.
Flavi, Toga and Retro are Icosahedral and enveloped.
Corona is Helical and enveloped.
Which DNA viruses are enveloped?
Hepadna, Herpes, Pox
Which virus is the biggest and most complicated? What kind of nucleic acid does it have?
Pox. Linear ds DNA that is X linked.
Which is larger, rabies or poliovirus? Which belongs to the Picornaviridae family and which belongs to the Rhabdoviridae?
Rabies is larger (170nm to 30nm)
Poliovirus is a Picornavirus, Rabies is a Rhabdovirus.
Which virus, out of Norovirus and Influenza virus would be hardier in the environment? Why?
Norovirus. It is a non-enveloped Calcivirus and much less fragile than the enveloped influenza virus (orthomyxovirus).
Which viruses are usually arboviruses?
Flavi, Toga, Bunya
Which virus contains 60 capsomers, each with one copy of four viral proteins?
Poliovirus (picornavirus)
Does Measles Virus enter a cell by endocytosis or fusion? What family of virus is it?
Fusion. Paramyxovirus.
What host receptors does Adenovirus interact with to enter a cell? Does it enter via fusion or endocytosis?
Integrin like Cell Adenovirus Receptors (CAR) via penton fibre. Endocytosis.
Which virus interacts has receptors in a “canyon” that interact with host cell CD155 before conformational changes in the VP1 capsid protein result in endocytosis?
Poliovirus.
What family of viruses have a double shelled capsid? How do these viruses enter a host cell (fusion or endocytosis) and what special particle is produced in the process? What is an example of a virus in this family that easily survives in the environment?
Reoviridae.
Receptor mediated endocytosis. Proteolytic modification of the capsid produces the Infectious Subviral Particle (ISVP)
Rotavirus.
Which viruses are in Baltimore class I? What does this mean?
Papova, Adeno, Hepadna, Herpes, Pox.
They have a dsDNA genome which is transcribed to form m+RNA.
Which viruses are in Baltimore class II? What does this mean?
Parvo.
It has a ssDNA genome which must become ds before m+RNA can be produced.
Which viruses are in Baltimore class III? What does this mean?
Reo.
It has a dsRNA genome which is converted to m+RNA.
Which viruses are in Baltimore class IV? What does this mean?
Calici, Picorna, Flavi, Toga, Corona.
They have +ssRNA which can immediately act as m+RNA
Which viruses are in Baltimore class V? What does this mean?
Filo, Rhabdo, Bunya, Orthomyxo, Paramyxo.
They have a –ssRNA genome which is a template for m+RNA
Which viruses are in Baltimore class VI? What does this mean?
Retro.
It has +ssRNA which is reverse transcribed to –DNA, then dsDNA before being integrated into the host genome and transcribed to m+RNA
Which DNA virus does not replicate in the nucleus?
Pox
Which virus has early genes transcribed in an anti-clockwise direction and late genes transcribed in a clockwise direction on the second strand of nucleic acid? What is an important product of the first viral mRNA and what does this protein do?
SV40 (Papovavirus).
Large T protein. Activates production of late genes/proteins by binding near the ORI and unwinding DNA.
What is Fork dsDNA replication? Which viruses use it?
DNA replication initiates at the ORI using a RNA primer and producing a leading and lagging strand.
Papova and Herpes.
What is displacement dsDNA replication? Which viruses use it?
Replication does not require a RNA primer (use protein, DNA hairpin) and there is no lagging strand.
Adeno and Parvo.
Which virus has an immediate early stage initiated by VP16? Which viral proteins that act on early gene expression are expressed as a result?
Herpes.
ICP4 and ICP0
What is the role of the terminal protein in viral DNA replication and which virus uses it?
Adeno.
Bound to 5’ end of each dsDNA strand and is primer for replication.
Which virus has ITRs to act as primers and templates for dsDNA synthesis from a ssDNA genome?
Parvo
Which virus contains its own RNA pol, DNA pol, capping enzyme, polyA polymerase? Does it carry splicing machinery? Where does it replicate?
Pox.
No.
Cytoplasm.
Which virus has double walled viral particles with outer envelope and inner capsid as well as incomplete particles with only envelope protein?
Hepatitis B (Hepadna)
Which virus makes pregenomic RNA that undergoes reverse transcription to make the dsDNA genome of extracellular virion?
Hepatitis B (Hepadna)
Which viruses have a genome with a 5’ cap and 3’ polyA tail?
Corona, Toga
Which virus has a genome with a 5’ cap but no 3’ polyA tail?
Flavi
Which virus has a genome with no 5’ cap, but a 3’ polyA tail?
Picorna
Which viruses make a dsRNA Replicative Intermediate during their replication cycle?
Calici, Picorna, Flavi, Toga, Corona
Which viruses make single mRNA and subgenomic mRNA?
Toga, Calici
Which virus has a 5’ cloverleaf, genomic CRE element and 3’ pseudoknot?
Poliovirus (picorna)
Which virus has a genome with complimentary 5’ and 3’ ends that allow cyclisation? What recognises the complex?
Flavivirus.
NS5 (RdRp and methyltransferase)
Which virus utilises a subgenomic promoter? What strand of RNA is transcribed from it? What kind of proteins does this lead to?
Toga.
Transcribes –strand to produce +RNA for structural proteins.
Which virus utilises RdRp skipping to produce a nested set of 8 discontinuous subgenomic RNAs in the cytoplasm?
Coronavirus
What kind of viruses can induce interferons and cytokines due to their replication method?
+ssRNA viruses. Process involves a dsRNA intermediate, foreign in human cells.
Which viruses have 5’ IRESs that interact with translational machinery? What kind of nucleic acid do these viruses have?
Poliovirus (picorna), Hepatitis C (flavi)
+ssRNA
Which virus makes a protease that degrades 5’ mRNA caps so that translation of viral proteins dominates translation of cellular proteins?
Poliovirus (picorna)
Which virus uses read-through translation and progressive proteolytic cleavage of RNA-replicase polyprotein to change the template preference of the enzyme?
Togavirus
Which virus is also known as Adeno-associated virus? What kind of nucleic acid does it have?
Parvovirus.
ssDNA
What are Rep78/68? Which virus uses them during replication?
Viral proteins that nick dsDNA and define the end of a genome.
Parvovirus.
Which virus has a dsDNA genome and can transcribe four different sized mRNAs that share a termination site?
Hepatitis B (Hepadnaviridae)
Which –ssRNA viruses have segmented genomes?
Ortho, Bunya
Which –ssRNA viruses have non-segmented genomes?
Filo, Rhabdo, Paramyxo
What kind of viruses must carry a virion polymerase in their capsid? What families have this kind of nucleic acid?
-ssRNA viruses
Filo, Rhabdo, Bunya, Orthomyxo, Paramyxo
What kind of virus has a genome made up of 8 –ssRNA segments? What important proteins does this virus carry in it’s virion?
Influenza (orthomyxo)
PB1, PA, PB2, (all 3 = RNP),
HA, NP (nucleocapsid protein), NA
MI (matrix), M2 (ion channel) (from spliced mRNA)
NS1, NEP/NS2 (capsid) (from spliced mRNA)
Which RNA virus is unique in its utilisation of the host nucleus during replication? Why does it do this?
Influenza (orthomyxo)
It “snatches” 5’ caps from cellular RNA so viral RNA is translated.
Which virus is dependent on the transcription of new host cell mRNAs?
Influenza (orthomyxo)
What is an ambisense virus? What are examples of this?
Segmented, negative strand viruses. Both NA strands encode proteins.
Bunya, Arena, Phlebo, Tospo, Tenu
What is a risk for dsRNA viruses? How is this overcome? What type of virus has a dsRNA genome?
dsRNA readily recognised as foreign, immune response.
Virus transcribe/replicate RNA concealed in inner core of virus. Prevents activation of IFN response.
Reo
Which virus contains a packing signal near the left IR and ori? What are features of this sequence? What viral protein recognises it?
complex, repeated sequences. Overlapping with enhancers that stimulate late transcription.IV2a
Which virus has a packaging signal in spliced regions to ensure that only genomic RNA is packaged as opposed to mRNAs?
HIV (retro)
Which viruses assemble their virions through the association of separately translated monomeric proteins? What structures assemble in this way for these viruses?
SV40 pentamer units
Adenovirus penton spikes
HBV capsid
Which viruses assemble their virions from polyprotein subunits that are refolded following proteolytic processing?
Poliovirus (picorna)
Retro
Which virus requires a chaperone protein to correctly fold virion structural proteins? Which chaperone does it use and what structures are formed?
Adenovirus
Viral L4 for hexon trimers
Which DNA virus has a RNA pre-genome and assembles in the cytoplasm?
Hepadna
What kind of nucleic acid is usually found in viruses that escape host cells via lysis?
DNA
What kind of viruses often import structural proteins into the nucleus before the can encapsidate their genome?
dsDNA
Which virus has concatemers on its genome? What important signals are found in these regions and what do they do?
Herpes Virus
HSC-1 packaing signals: pac1, pac2
Allow genome to be recognised and cleaved in DR1 so it can be encapsidated.
Which virus utilises viral scaffolding proteins during genome packaging? How is scaffold removed?
Herpesvirus Viral protease (VP24)
The 5S structural unit is a feature of which virus? Which proteins are in it and what are they cleaved by?
Poliovirus (picorna)
VP2 and 4 (VP0), VP3, VP1
Cleaved by 3CDpro viral protease
Which virus assembles in the rER lumen before exiting the cell via the golgi and recycling endosome and exocytosis?
Flavivirus
Which virus relies on host Furin to cleave prM to M in order to prevent its envelope fusing with cellular membranes?
Flavivirus
Which virus assembles at the cell membrane due to the accumulation of TM-SU and myr-MA-GAG I lipid rafts?
HIV (retro)
Which virus hijacks host microtubules and actin to exit the cell?
Vaccina (pox)
Which virus assembles its capsid in the nucleus before going through envelopment/de-envelopment through the nuclear membrane and final assembly via budding through the golgi and exiting via exocytosis?
Herpesvirus
