Wk 3 - Viruses - Baltimore Classification System

Question 1

Class I

- Ex: herpesvirus

Answer 1

• dsDNA
• Semiconservative replication
• Enveloped
• Invasion/cycle
  1. Capsid injects dsDNA into nucleus
  2. Use host DdRp to do mRNA synthesis
  3. Proteins translated - some of these involved in replication of viral DNA
  4. Buildup of made capsid protein -> package DNA in it
  5. Add envelope and glycolipids in ER and golgi and transfer out

Question 2

Class IV

- Ex: picornavirus (poliovirus)

Answer 2

• ssRNA (+) sense
• !!! Need to go through translation first before can replicate genome (even though it’s in the proper sense strand)
• 1 of the proteins is an RdRp - this is what does replication…
• Translation product = ~10 proteins

Question 3

Class V

Ex: Orthomyxoviruses (Influenza)

Answer 3

• ssRNA (-) strand
• Can’t translate right away because (-) strand
• Makes (+) strand right away… Genome is packed in virus particle with the RdRp attached so as soon as it enters the host cell it can make a (+) sense strand
• (+) strand translated into proteins
• Fun fact… flu steals 5’ cap so it can leave nucleus as stable mRNA… bitch.

Question 4

Class VI

Answer 4

• 2 copies of (+) ssRNA
• Life cycle
  1. Particle shoots genetic material into cytoplasm
  2. Reverse transcriptase activated
  3. RdRp takes RNA and turns it into circular DNA
  4. Integrase integrates the DNA into host chromosome (this is a provirus form)… Once it’s integrated it’s there forever :(
  5. Translates viral proteins to go on and make new capsids
  6. Replicated info packed and released as ssRNA to go and infect a new host

Question 5

Class II

Answer 5

ssDNA in (+) strand

Question 6

Class III

Answer 6

dsRNA in the (+) strand

Question 7

Class VII

Answer 7

dsDNA in the (+) sense
Reverse transcriptase (RdDp)