virology

Question 1

general properties of viruses

Answer 1

• Obligate intracellular parasite
• Host specific
• Size 10- 300 or 400 nm
• Genetic material either DNA or RNA • Unable to grow on synthetic media

Question 2

classifications of viruses

Answer 2

• DNA - single or double stranded
enveloped or non-enveloped

• RNA - single or double stranded
enveloped or non-enveloped

Question 3

baltimore scheme classications

Answer 3

– Class 1, double stranded DNA (ds DNA)
– Class 2, single stranded DNA (ss DNA)
– Class 3, double stranded segmented RNA (dsRNA)

– Class 4, single stranded RNA (ss RNA) positive sense
– Class 5, single stranded RNA (ss RNA) negative sense

– Class 6, ss RNA positive sense with dsDNA (retroviruses) intermediate before replication
– Class 7, ds DNA, part ss DNA, with ss RNA intermediate (reversiviruses)

Question 4

baltimore scheme is based on what

Answer 4

nucleic acid

Question 5

structure of types of virion

Answer 5

• A nucleic acid core (DNA or RNA)
• A capsid - capsomeres
  * Shape determination
  * Nucleic acid protection
  * Facilitates attachment
  * Antigenic material
• With or without envelope (naked)
  * Enveloped with or without spikes

Question 6

virion structure description

Answer 6

nucleic acid in middle (twirl thing)

capsomeres - capsid subunits - hex gate, blue dot dot design

capsid protein coat - glue around inside envelope

envelope (membrane)

Spikes (projections) - pinned to envelope

Question 7

morphological types

Answer 7

helical (round and round layers helix dot dot)

icosahedral - hex diamond

complex (undefined) - ummmm spider

Question 8

reproduction + effects on host

Answer 8

• Inside host cells
• Host produces new viral particles
• Produce cytopathic effects
• Bacteriophage (phage) are viruses that infect bacteria
– Can be used to type bacteria
– As treatment instead of antibiotics?

Question 9

replication stages and stuff

Answer 9

• Attachment
– To host cell via specific receptor on cell membrane

• Penetration
– Entry into host cell (internalization)
– “Uncoats”–shedding protein shell

• Replication of viral genome
– This varies between viral types
– production of viral mRNA
– Production of early viral proteins

• Production of late viral proteins (structural)
• Assembly of the progeny virions
• Release of virions from cell (budding or lysis)

Question 10

viruses cause disease by 2 mechanisms…

Answer 10

1. Replication within the host cell leading to direct damage of the cell
2. Host defenses leads to cell damage as it attempt to clear the virus infected cells

Question 11

types of viral infections

Answer 11

• Mild
• Latent
• Severe
• Chronic
• Oncogenic (certain genotypes of Papillomavirus)
• Teratogenic (Rubella)

Question 12

mode of transmission

Answer 12

• Physical contact - direct or indirect 
• Air borne
• Food-borne
• Arthropod-borne
         viruses transmitted by arthropods are termed Arbovirus, this is not a taxonomic term
• Direct inoculation 
• Intra-placental