Micro Quiz 11/3

  1. Disease
    • Term coined by Pasteur to describe the spoilage of beer and wine
    • A virus is a disease-causing agent
  2. Discovery of Virus
    • Pasteur 1884(rabies)
    • Mayer 1886(Tobacco Mosaic Virus)
    • Could not isolate the disease-causing agent by means used for bacteria
    • Disease-agent could not be killed by EtOH
    • Could not be cultured in media that supports bacterial growth*
    • Could only proliferate in growing tissue
  3. Viruses
    • The term virus (Latin for poisonous substance) was used to describe a disease-causing substance that is not a bacteria
    • Fundamentally different from cellular forms of life
    • The first virus ever seen - Tobacco Mosaic Virus (1935)
  4. Viruses Characteristics
    • Genetic material in a protein coat
    • Naked
    • enveloped
  5. Viruses: Genetic Material
    • ssRNA, dsRNA, ss cDNA, ss DNA, ds DNA, ds cDNA.
    • Living things are double stranded DNA all the time
  6. Viruses:
    Obligate Parasites
    • Must be inside host cell to reproduce
    • Lack all metabolic machinery: ribosomes, most enzymes
    • Hijack host’s metabolism
  7. Viruses: Host Specificity
    • Host range
    • Plant
    • Bacterial (bacteriophage (bacteria eater); phage)
    • Animal
    • Specificity based on “fit” between viral proteins and host receptors
    • 3D specificity
    • Plant and Bacterial are naked. Animal are almost always enveloped. This looks just like our cells so they fit right in.
  8. Viruses: Mode of Infection
    • Infection: entry into host cell
    • Mechanisms vary:
    • Phage inject NA
    • Receptor-mediated endocytosis
    • Facilitated diffusion
    • Active transport
  9. Viruses: Capable of Self-Assembly
    • Take over host’s resources and machinery
    • To make viral proteins (capsid) and nucleic acids
    • Self-assembly
  10. Viruses Characteristics (Distinction)
    • Each virus is distinct in:
    • Nucleic acid
    • Capsid structure
    • Host range
    • Mode of infection
  11. Viruses: General information
    • Infectious particles: nucleic acid in a protein coat
    • Naked or enveloped
    • Obligate parasites
    • Host range
    • Mode of infection
    • Capable of self-assembly
  12. Viruses are non-living
    • Cell theory: cell is smallest unit of life
    • Viruses are acellular (do not have cells)
    • Lack all cellular machinery
    • Cannot replicate outside a host
    • Do not ALWAYS have their genetic material in the form of ds DNA
    • Do not have all the characteristics of living things

    Organization, metabolism, homeostasis, grow/develop/reproduce, adapt, evolve. If you can’t say yes to every single one, you are not a living thing.
  13. +/- strand
    • (+)strand: coding
    • (-)strand: noncoding
    • (-) strand viral RNA must first be copied [(+) strand] before it can be translated
  14. Growing Viruses
    • Phage:
    • Plaque method
    • Animal viruses
    • In animals
    • In eggs
    • Cell culture
  15. Cytopathic Effects of Selected Viruses
    • Cytocidal (cell death)
    • Acidophilic inclusion bodies in nucleus
    • Basophilic inclusion bodies in nucleus
    • Acidophilic inclusion in cytoplasm
    • Cell fusion
    • Transformation
    • Destruction of T cells
  16. Viral Replication
    • Viruses can only replicate inside a host cell
    • Usually follow a one-step growth curve

    eclipse period, virus released from host, acute infection, death
Card Set
Micro Quiz 11/3