Virology Quiz #1 Flashcards
What is the definition of a virus?
Chemical complexes of RNA or DNA protected by protein
Why are viruses not cells?
- They cannot synthesize their own ATP, aa’s or nucleotides
- (therefore they cannot replicate without a host cell)
Can viruses carry out translation or transcription independently?
No- requires ATP and nucleotides from host cell
What are the three ways that the genetic information can progress?
- DNA-RNA-protein
- RNA-RNA-protein
- RNA-DNA-RNA-protein
What are the three kinds of virus “shapes”
Helical, icosahedral, complex
What are the types for virus genetic material?
RNA: Linear single stranded, linear double stranded, circular single stranded, circular double stranded
DNA: Linear single stranded, linear double stranded, circular single stranded, circular double stranded
What is a capsid made out of?
Protein
Where is the gene that encodes the protein structure that is called the capsomere?
In the virus’ genome
What is a virus envelope made out of?
Lipid bilayer— derived from plasma membrane or any other membrane structure
What is the purpose of envelope glycoproteins?
Required for attachment to the host cell
Where does the envelope structure come from?
Stolen from the host cell
What is the difference between enveloped and naked viruses?
Enveloped: virus buds through the membrane and acquires the envelope without killing the host cell immediately— virus replication occurs for prolonged periods of time
Naked: cell lysis, all progeny is released
What are the two general pathways of virus evolution?
Co-evolution with host and infection of multiple host species
What are the advantages and disadvantages of co-evolution with host?
Advantage: prosperous host=prosperous virus
Disadvantage: host becomes extinct, so does virus
(Smallpox)
What is the advantage or disadvantage of Infection of multiple host species
Advantage: of one host species is compromised, virus can replicate in another
Disadvantage: cannot optimize for any one situation
What are the steps of all virus replication cycles?
- Virus adsorption/ attachment to host cell
- Genome (and any needed proteins) enter the cell
- Gene expression (Making the parts): Synthesis of viral mRNA, viral proteins, replication of genome
- Assembly of virus from parts
- Release from host cell
What is a nucleocapsid?
A capsid with enclosed genome
What are some additional layers that a virus an have besides capsid?
- lipid bilayer envelope
- layer of protein between capsid and envelope
- internal lipid layers
- protein occlusion bodies
What is the function of the capsid?
- Protection for the genome
2. Delivery of virus’ genome to the location within the cell where the genome can be replicated and expressed
What part of the virus particle binds to the host cell?
Naked: capsid structure to bind to the host cell
Envelope: envelope has structure to bind to host cell— (not capsid)
What is required for a host cell to bind to a virus?
- both must have complementary structures to interact (host cell has virus receptor, and virus has anti-receptor)
What are the different strategies for a virus to put its genome into the cell?
- only the genome enters the cell
- the virus enters the cell in an endosome, genome is released to cytoplasm/nucleus
- the virus envelope fuses to cell membrane, releasing genome into cytoplasm/nucleus
Why is the capsid both stable and unstable?
Stable: to persist in environment
Unstable: allow for the release of the genome into the cell’s cytoplasm
What might cause the capsid to change from a stable structure to an unstable structure?
Interaction with other proteins, changes in pH, cleavage of proteins, unfolding of proteins
What is adsorption?
Random weak collisions that lead to attachment of the virus particle to the virus receptor
What is attachment?
multiple molecular interactions that lead to a firm binding so that the virus’ genome can enter the cell
What makes a host cell susceptible and permissive?
Susceptibility: ability for virus to get its genome into the host cell (cell surface structure)
Permissiveness: ability of the virus to replicate its genome in the host cell
What is CD155
The poliovirus receptor that lives on human cells
