Microbiology: Viruses Flashcards Preview

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Flashcards in Microbiology: Viruses Deck (14):

Viral genetics:


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


Viral genetics:


viruses with segmented genomes exchange segments

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


Viral genetics:


  • 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


Viral genetics:

Phenotypic mixing

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


Viral Vaccines:

Live attenuated vaccine

  • 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*



Viral Vaccines:


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

*SalK= Killed*

*RIP Always*


Viral Vaccines:


HBV (antigen=recombinant HBsAg)

HPV (6, 11, 16, 18)


DNA viral genomes

  • 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*


RNA viral genomes

  • 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*


Naked viral genome infectivity

  • 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


Viral replication: Location

DNA viruses

RNA viruses

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


Naked viruses

  • 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*


DNA viruses

  • 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)