Term
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Definition
| A submicroscopic entity consiting of a single nucleic acid surrounded by a protein coat, only capable of replication within ithe cells of plants and animals |
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Term
| What is a virus composed of? |
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Definition
RNA / DNA
Single or double stranded
One molecule or segmented (multiple separate strands) |
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Term
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Definition
To encode 3 - 100s of proteins
Genes encode structural proteins and non structural proteins |
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Term
| Name the functions of a nonstructural protein |
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Definition
Act with cellular enzymes to replicate virus.
May switch off host cell activities.
Block immune system. |
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Term
| What is the function of the capsid surrounding the viral DNA / RNA? |
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Definition
To protect the viral DNA / RNA from degradation.
May have protein spikes on the surface to allow attachment to cells. |
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Term
| What is the function of the lipid envelope that surrounds some viruses? |
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Definition
| Contains viral proteins which are required for the virus to attach to and infect a new cell. Non-enveloped viruses attach and infect the cell directly via capsid. |
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Term
| What is the life cycle of a virus? |
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Definition
| Attachment --> Entry --> Replication and protein synthesis --> Assembly --> Release |
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Term
| Describe the basis of virus classification. |
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Definition
| Viruses cannot be classified by disease. Viruses are classified by their replication stratergy, nucleic acid and similarity of nucleic acid sequence. |
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Term
| How does the Baltimore Classification classify viruses? |
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Definition
DS DNA, DS RNA, SS DNA, SS RNA - positive sense / negative sense / use reverse transcription.
Can be further classified by family, serotypes and genotypes. |
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Term
| State the basis of double stranded DNA virus replication. |
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Definition
| By entering the host nucleus and often requiring host cell polymerases to replicate with genomes. Some viruses encode their own replication factors. |
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Term
| State the basis of single stranded DNA virus replication. |
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Definition
| They replicate within the nucleus and form a double-stranded DNA intermediate during replication. |
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Term
| State the basis of double stranded RNA virus replication. |
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Definition
| Replication is monocistrtonic and includes individual, segmented genomes, meaning that each of the genes codes for only one protein, unlike other viruses which exhibit more complex translation. There is no reliance on host polymerases. |
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Term
| State the basis of single stranded positive sense RNA virus replication. |
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Definition
| Replication occurs in the cytoplasm and is either polycistronic or complex transcription. |
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Term
| State the basis of single stranded negative sense RNA virus replication. |
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Definition
| Cannot be directly accessed by host ribosomes to immediately form proteins. Instead, they must be transcribed by viral polymerases into "readable" complementary positive sense strands. |
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Term
| What challenges are there to developing effective anti-viral drugs? |
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Definition
Multiple viral genotypes / serotypes.
Viral mutation and viral resistance.
Much of the viral life cycle relies on the host cell - potential for substances active against viruses to also have host cell effects. |
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Term
| What are the seven stages of the virus life cycle? |
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Definition
Attachment
Entry
Replication
Integration (retrovirus)
Protein synthesis
Assembly
Viral release |
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Term
| What does attachment of a virus involve? |
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Definition
| Specific interaction between a protein on the virus surface and the host cell. Determines which cells the virus effects. Partly responsible for disease manifestations. |
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Term
| Potential points of antiviral action during attachment are... |
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Definition
Binding to the viral receptor
Binding to the cellular receptor |
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Term
| What does entry of a virus involve? |
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Definition
| Virus is taken up into the cell. Depends on cellular processes and confromational changes in the viral capsid. |
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Term
| Potential points of antiviral action during entry are... |
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Definition
Blocking fusion between virus envelope and cell membrane
Fix the viral capsid in a conformation which prevents entry. |
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Term
| What does replication of a virus involve? |
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Definition
| Nucleic acid is copied - most viruses encode their own DNA polymerase or RNA polymerase or reverse transcriptase. |
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Term
| Most antiviral currently avaliable target which part of the virus life cycle? |
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Definition
| Replication - viral DNA polymerase inhibitors and reverse transcriptase inhibitors. |
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Term
| What does integration of a virus involve? |
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Definition
| Viral DNA is integrated into the host chromosome as an essential part of retroviral replication strategy. |
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Term
| What does protein synthesis of a virus involve? |
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Definition
| Making viral proteins using host cell processes. |
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Term
| Which stage of the viral life cycle is not good to target antiviral treatment towards? |
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Definition
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Term
| What does assembly of a virus involve? |
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Definition
| Viral proteins coming together with viral nucleic acid and new viral particles are formed. There are no current therapies targeting this stage. |
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Term
| What does viral release of a virus involve? |
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Definition
| Viral particles are released from the cell and are free to infect other cells. Some viruses acquire their lipid envelope during this process. |
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Term
| What part of the viral life cycle to influenzavirus neurominidase inhibitors act upon and what is their mechanism of action? |
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Definition
They act on the viral release stage of the viral life cycle.
They prevent viral release from the cell, leaving virions tethered to the cell and unable to infect other cells. |
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