Introduction to virology
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Introduction to Virology. I. Objectives. What is a virus How do viruses multiply How are viruses classified (What are some of the diseases viruses cause). II. Historical Perspective. A. Ancient times 1. poliovirus 2. smallpox B. More recent history 1. 1790’s Iwanowski 2. 1890’s

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Introduction to Virology

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Introduction to Virology


I. Objectives

  • What is a virus

  • How do viruses multiply

  • How are viruses classified

  • (What are some of the diseases viruses cause)


II. Historical Perspective

  • A. Ancient times

    • 1. poliovirus

    • 2. smallpox

  • B. More recent history

    • 1. 1790’s

      • Iwanowski

    • 2. 1890’s

      • Jenner


III. What is a virus?

  • A. Characteristics


B. Comparison to bacteria1. overall

  • Bacteria Virus

  • Intracellular parasite (no) yes

  • Plasma membraneyes no

  • Binary fission yes no

  • Filterable no yes

  • Possess DNA & RNAyes no

  • ATP production yes no

  • Ribosomesyes no

  • Antibiotic sensitive yes no


  • 2. Growth comparison

  • 3. Size comparison

  • 4. Genome size comparison


IV. Nucleocapsid morphology


  • A. Helical

  • B. Polyhedral

  • C. Complex


V. How viruses multiply (13.10)

  • 1. Basic strategy

    • Attachment

    • Penetration

    • Synthesis of viral proteins and nucleic acids

    • Maturation

    • Release


2. Bacterial viruses: Fig 13.12

  • Lytic vs lysogenic cycle


3. General Animal Virus Multiplication


a.Virus Budding: Fig 13.20


4. Differences in lab culture of viruses

  • a. bacteriophage

  • b. animal viruses


VI. Differences in multiplication due to differences in genome organization

  • A. Genome organization


B. DNA Viruses: Life Cycle: Fig 13.17


C. Replication of RNA viruses: Fig 13.17


VI. Classification schemes

  • A. Formal taxonomies

  • B. Baltimore Classification


C. Nucleic acid type --> Baltimore classification

  • Class I

    • ds DNA

  • Class II

    • ssDNA (positive and negative)

  • Class III

    • dsRNA

  • Class IV

    • ssRNA (positive)


  • Class V

    • ssRNA (negative)

  • Class VI

    • ssRNA (positive, replication intermediate DNA)


1. Class I: dsDNA Viruses

  • Bacterial

    • Bacteriophage

  • Plant

    • Caulomoviridae


  • Human

    • Herpesviridae

    • Adenoviridae

    • Poxviridae

    • Papovaviridae

      • Papillomavirus

      • Polyomavirus

      • Vacuolating agent


  • Hepadnaviridae

    • After protein synthesis, DNA replicated through RNA intermediate


2. Class II: ssDNA viruses

  • Bacteria

  • Plant

  • Animal


3. Class III: dsRNA viruses

  • Reoviridae


4. Class IV: ss (+) RNA viruses

  • Picornaviridae

  • Togaviridae

  • Flaviviridae

  • Coronaviridae

  • Calciviridae


5. Class V: ss (-) RNA viruses

  • Rhabdoviridae

  • Filoviridae

  • Paramyxoviridae

  • Orthomyxoviridae

  • Bunyaviridae

  • Deltaviridae

  • Arenaviridae


Retrovirus Life Cycle: Fig 13.19


6. Class VI: ss (+) viruses (dsDNA intermediate)

  • Retroviridae

    • Oncoviruses

    • Lentivirus


D. Review of Replication Strategies


VII. Effects of Viral Infection on Cell


VIII. Oncogenic Viruses


IX. Plant viruses

  • Morphologically similar to animal viruses

  • Enter through wounds or parasites

  • Some multiply in insects


X. Viroids

  • Plant pathogens

    • infectious naked RNA

  • 20-25 identified so far

  • ss covalent circle


XI. Prions

  • A. Fig 13.21

  • B. PrPC vs PrPSc

    • Structural differences

    • Detergent solubility differences

    • Differences in susceptibility to protein degrading enzymes


Prion diseases of humans and animals


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