Term
| What are the steps in the viral replication cycle? |
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Definition
1) Recognition and attachment to the host cell surface
2) Penetration and uncoating
3) Macromolecular synthesis
4) Assembly
5) Budding and release |
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Term
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Definition
| Viral Attachment Proteins on the surface of the virion capsid that are recognized by receptors on cells |
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Term
| What are the three mechanisms for viral penetrations? |
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Definition
1) Direct penetration
2) Fusion at the plasma membrane
3) Receptor-mediated endocytosis |
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Term
| Why is uncoating important? |
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Definition
| It gives the viral genome access to the replication site |
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Term
| How is uncoating initiated and promoted? |
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Definition
| It is initiated by attachment to the receptor, and it is promoted by acidic environment or proteases in endosomes or of viral origin |
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Term
| Where can uncoating occur? |
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Definition
| At the plasma membrane, within endosomes, or at the nuclear membrane |
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Term
| Why can viral particles not be detected immediately after infection? |
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Definition
| The virus is still docking and uncoating |
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Term
| Which RNA viruses replicate in the cytoplasm? |
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Definition
| Influenza viruses and retroviruses |
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Term
| Can host cells replicate RNA? |
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Definition
| No, viruses must encode and RNA-dependent RNA polymerase |
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Term
| Why are RNA viruses prone to infection? |
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Definition
| They lack proofreading ability and are thus prone to mutation |
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Term
| What is the key event in viral replication? |
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Definition
| The synthesis of viral proteins by the host based on an mRNA presented by the virus |
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Term
| How are Class 1 viral proteins synthesized (Picornaviruses)? |
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Definition
| One +RNA makes one long protein that gets cleaved |
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Term
| How are Class 2 viral proteins synthesized (Coronaviruses)? |
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Definition
| One +RNA makes several individual proteins |
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Term
| How are Class 3 viral proteins synthesized (Paramyxoviruses)? |
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Definition
| One -RNA is transcribed into multiple +mRNA strands to make individual proteins |
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Term
| How are class 4 viral proteins synthesized (Orthomyxoviruses)? |
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Definition
| Segmented -RNA is transcribed into segmented +mRNA to make multiple proteins |
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Term
| How are class 5 viral proteins synthesized (Reoviruses)? |
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Definition
| dsRNA use the - strand to transcribe +mRNA and make multiple proteins |
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Term
| How are class 6 viral proteins synthesized (Arenaviruses)? |
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Definition
| Individual +mRNA strands are made are made from the + and - segments to make individual proteins |
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Term
| How are class 7 viral proteins synthesized (Retroviruses)? |
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Definition
| They must be reverse-transcribed into DNA and then inserted into the host genome to make proteins that are subsequently cleaved |
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Term
| Which RNA viruses are positive-stranded? |
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Definition
| Picorna-, toga-, flavi-, calici-, and coronaviruses |
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Term
|
Definition
| A -RNA strand must be made to synthesize new +RNA strands |
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Term
| Which -RNA viruses are segmented? |
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Definition
| Orthomyxo-, bunya- and arenaviruses |
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Term
| Which -RNA viruses are non-segmented? |
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Definition
| Paramyxo-, rhabdo-, and filoviruses |
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Term
| Which -RNA viruses are ambisense? |
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Definition
| Arena- and some bunyaviruses |
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Term
| Which RNA viruses are double stranded? |
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Definition
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Term
| How do reoviruses replicate their RNA? |
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Definition
| They are unable to use the viral RNA as mRNA, so they must first transcribe +mRNA in cores and they make a complementary strand |
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Term
| What happens to the retrovirus genome? |
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Definition
| It must be converted into DNA by the reverse transcriptase carried by the virions in the core |
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Term
| What mechanisms might RNA viruses use to enhance translation and virility of viral genomes? |
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Definition
| They may have internal ribosomal entry sites, cleave cap-binding protein, or destroy cellular mRNAs |
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Term
| What modifications might be made to viral proteins after translation? |
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Definition
| Glycosylation, phosphorylation, and acylation |
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Term
| How are non-enveloped RNA viruses assembled? |
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Definition
| The empty capsid is assembled and later the genome is packaged |
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Term
| How are enveloped RNA viruses assembled? |
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Definition
| Matrix proteins align the inside of the plasma membrane at the same location as glycoproteins outside the plasma membrane. Viral RNA buds out with the proteins until they are all pinched off as a new virus |
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