Flashcards in Virology Deck (21):
What are characteristics of a virus?
1. Acellular infectious agent2. Nucleic acid surrounded by a protein coat3. Obligate parasite4. 20-300nm in size
What are the components of a virus?
1. Genome2. Capsid3. Matrix / integument*4. Envelope*5. Viral attachment proteins*Only some viruses have these
What are +sense ssRNA molecules?
Are in the correct orientation to direct protein synthesis; from their genome they can generate a template for a ribosome
What are -sense ssRNA molecules?
1. Cannot be used directly for a template for directing protein synthesis2. Need to generate a +sense mRNA molecule
Which virus families have a ssDNA genome?
1. Parvoviridae2. Papovaviridae3. Adenoviridae
Which virus families have a dsDNA genome?
1. Herpesviridae2. Poxviridae3. Hepadnaviridae
What are properties of RNA viruses?
1. RNA is labile and transient2. Replicate in cytoplasm3. Must encode an RNA-dependent RNA polymerase4. Must carry polymerases (except +RNA genome)5. Prone to mutation
What are properties of naked capsids?
1. Environmentally stable2. Released from cell by lysis3. Spread easily4. Dry out and maintain infectviity5. Survive gut conditions6. Resistant to detergents
What are properties of envelopes?
1. Environmentally labile2. Modifies cell membrane during replication3. Released by budding and lysis4. Must stay wet5. Cannot survive GI tract6. Spreads in large droplets, secretions, blood7. Does not need to kill cell to spread
What are the stages of the virus life cycle?
1. Attachment2. Entry3. mRNA production4. Protein and genome synthesis 5. Virion assembly6. Egress
What is the biggest challenge with viral genome replication for DNA?
Cellular DNA replication machinery is not available at all times
What are the solutions to cellular machinery unavailability for DNA?
1. Make cellular DNA replication machinery available via growth stimulation 2. Encode viral proteins to synthesize genome
What is the biggest challenge with viral genome replication for RNA?
No cellular RNA dependent RNA polymerase
What are the solutions to cellular machinery unavailability for RNA?
1. Encode RNA dependent RNA polymerase in genome2. Encode RNA dependent RNA polymerase in genome AND carry the enzyme in virion
What are the properties of budding?
1. Occurs when you have assembly at the plasma membrane 2. Envelope proteins form into a patch on the plasma membrane and then recruiting some other tegument proteins and the genome to that portion of the membrane3. Protrusion and budding occurs
What is the primary diagnostic technique to identify infectious viruses?
What are the properties of the plaque assay?
Detects: infectious virusAdvantages: positivity shows active viral infectionLimitations: Restricted to viruses that replicate in tissue culture and produce cytopathic effect
What are the properties of antigen detection, ELISA?
Detects: viral proteins and glycoproteinsAdvantages: sensitive and quickLimitations: requires specific antibody
What are the properties of PCR?
Detects: DNA genomesAdvantages: highly sensitiveLimitations: DNA sequence information must be available
What are the properties of rtPCR?
Detects: RNA genomesAdvantages: highly sensitiveLimitations: RNA sequence information must be available