Virology

Question 1

What are characteristics of a virus?

Answer 1

1. Acellular infectious agent2. Nucleic acid surrounded by a protein coat3. Obligate parasite4. 20-300nm in size

Question 2

What are the components of a virus?

Answer 2

1. Genome2. Capsid3. Matrix / integument4. Envelope5. Viral attachment proteins*Only some viruses have these

Question 3

What are +sense ssRNA molecules?

Answer 3

Are in the correct orientation to direct protein synthesis; from their genome they can generate a template for a ribosome

Question 4

What are -sense ssRNA molecules?

Answer 4

1. Cannot be used directly for a template for directing protein synthesis2. Need to generate a +sense mRNA molecule

Question 5

Which virus families have a ssDNA genome?

Answer 5

1. Parvoviridae2. Papovaviridae3. Adenoviridae

Question 6

Which virus families have a dsDNA genome?

Answer 6

1. Herpesviridae2. Poxviridae3. Hepadnaviridae

Question 7

What are properties of RNA viruses?

Answer 7

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

Question 8

What are properties of naked capsids?

Answer 8

1. Environmentally stable2. Released from cell by lysis3. Spread easily4. Dry out and maintain infectviity5. Survive gut conditions6. Resistant to detergents

Question 9

What are properties of envelopes?

Answer 9

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

Question 10

What are the stages of the virus life cycle?

Answer 10

1. Attachment2. Entry3. mRNA production4. Protein and genome synthesis 5. Virion assembly6. Egress

Question 11

What is the biggest challenge with viral genome replication for DNA?

Answer 11

Cellular DNA replication machinery is not available at all times

Question 12

What are the solutions to cellular machinery unavailability for DNA?

Answer 12

1. Make cellular DNA replication machinery available via growth stimulation 2. Encode viral proteins to synthesize genome

Question 13

What is the biggest challenge with viral genome replication for RNA?

Answer 13

No cellular RNA dependent RNA polymerase

Question 14

What are the solutions to cellular machinery unavailability for RNA?

Answer 14

1. Encode RNA dependent RNA polymerase in genome2. Encode RNA dependent RNA polymerase in genome AND carry the enzyme in virion

Question 15

What are the properties of budding?

Answer 15

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

Question 16

What is the primary diagnostic technique to identify infectious viruses?

Answer 16

Plaque assay

Question 17

What are the properties of the plaque assay?

Answer 17

Detects: infectious virusAdvantages: positivity shows active viral infectionLimitations: Restricted to viruses that replicate in tissue culture and produce cytopathic effect

Question 18

What are the properties of antigen detection, ELISA?

Answer 18

Detects: viral proteins and glycoproteinsAdvantages: sensitive and quickLimitations: requires specific antibody

Question 19

What are the properties of PCR?

Answer 19

Detects: DNA genomesAdvantages: highly sensitiveLimitations: DNA sequence information must be available

Question 20

What are the properties of rtPCR?

Answer 20

Detects: RNA genomesAdvantages: highly sensitiveLimitations: RNA sequence information must be available

Question 21

What are the properties of serology?

Answer 21

Detects: anti-viral antibodiesAdvantages: sensitive and quickLimitations: must allow for immune response and differentiate between past and current infections