Microbiology: Viruses

Question 1

Viral genetics:

Recombination

Answer 1

exchange of genes between 2 chromosomes by crossing over within regions of significant base sequence homology

Question 2

Viral genetics:

Reassortment

Answer 2

viruses with segmented genomes exchange segments

• influenza
• high frequence recombination
• cause of worldwide influenze pandemics

Question 3

Viral genetics:

Complementation

Answer 3

• When 1 of 2 viruses tha tinfect the cell has a mutation that results in a non-functional protein
• nonmutated virus complements the mutated one by making a functional protein the serves both viruses

Question 4

Viral genetics:

Phenotypic mixing

Answer 4

Occurs with simultaneous infection of a cell with 2 viruses

• Genome of virus A can be partically or completely coated ( pseudovirus) with the surface protein of B
• Type B protein coat determines the tropism (infectivity) of the hybrid virus
• progeny from infection have a type A coat that is encoded by type A genetic material

Question 5

Viral Vaccines:

Live attenuated vaccine

Answer 5

• induce humoral and cell mediated immunity but have reverted to virulence on rare occasions
• killed/ inactivated vaccines induce only humoral immunity but are stable
• no booster needed
• Live attenuated
  
  • Smallpox
  • yellow fever
  • Chicken pox ( VZV)
  • Sabin polio virus
  • MMR (Measles, Mumps, Rubella)
  • Influenza (intranasal)

* Live! One night only see small yellow chickens get vaccinated with Sabin and MMR! Its Incredible*

Question 6

Viral Vaccines:

Killed

Answer 6

• Rabies
• Influenza (injected)
• Salk Polio
• HAV vaccines

*SalK= Killed*

*RIP Always*

Question 7

Viral Vaccines:

Recombinant

Answer 7

HBV (antigen=recombinant HBsAg)

HPV (6, 11, 16, 18)

Question 8

DNA viral genomes

Answer 8

• All DNA viruses except parvoviridae are dsDNA
• All are linear except papilloma, polyoma and hepadnaviruses (circular)

* All are dsDNA like us, except “part-of-a-virus* is ssDNA*

Question 9

RNA viral genomes

Answer 9

• All RNA viruses except Reoviridae are ddRNA
• All are ssRNA like our mRNA, except repeato-virus (reovirus) is dsRNA
• positive stranded RNA viruses
  
  • retrovirus
  • togavirus
  • flavivirus
  • Coronavirus
  • Hepevirus
  • Calicivirus
  • picornavirus

* I went to a retro toga party where I drank flavored Corona and ate hippy California pickles*

Question 10

Naked viral genome infectivity

Answer 10

• Purified nucleic acids of most dsDNA ( except poxviruses and HBV) and postive strand ssRNA viruses are infectious
• Naked nucleic acids of negative strand ssRNA and dsRNA viruses are NOT infectious
  
  • require polymerases contained in complete virion

Question 11

Viral replication: Location

DNA viruses

RNA viruses

Answer 11

• DNA: all in nucleus except poxvirus
• RNA: all in cytoplasm except influenza and retrovirus

Question 12

Naked viruses

Answer 12

• Papillomavirus
• Adenovirus
• Parvovirus
• Polyomavirus
• Calicivirus
• Picornavirus
• Reovirus
• Hepevirus

(most acquire envelope from cell membrane, except herpesvirus which get envelopes from nuclear membrane)

*Give PAPP smears and CPR to a naked Heppy*

*DNA =PAPP, RNA= CPR and Hepevirus*

Question 13

DNA viruses

Answer 13

• Hepadna
• Herpes
• Adeno
• Pox
• Parvo
• Papilloma
• Polyoma

Double stranded: except parvo (ssDNA)

Linear: except papilloma and polyoma (circular, supercoiled) and hepadna (circular, incomplete)

Icosahedral: Except pox (complex)

Replicate in nucleus: Except pox (has own DNA dependent RNA polymerase)

* HHAPPPPy*