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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I objectives
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
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
III. What is a virus?

  • A. Characteristics


B comparison to bacteria 1 overall
B. Comparison to bacteria1. overall

  • Bacteria Virus

  • Intracellular parasite (no) yes

  • Plasma membrane yes no

  • Binary fission yes no

  • Filterable no yes

  • Possess DNA & RNA yes no

  • ATP production yes no

  • Ribosomes yes no

  • Antibiotic sensitive yes no





V how viruses multiply 13 10
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
2. Bacterial viruses: Fig 13.12

  • Lytic vs lysogenic cycle




4 differences in lab culture of viruses
4. Differences in lab culture of viruses

  • a. bacteriophage

  • b. animal viruses


Vi differences in multiplication due to differences in genome organization
VI. Differences in multiplication due to differences in genome organization

  • A. Genome organization


B dna viruses life cycle fig 13 17
B. DNA Viruses: Life Cycle: genome organizationFig 13.17


C replication of rna viruses fig 13 17
C. Replication of RNA viruses: genome organizationFig 13.17


Vi classification schemes
VI. Classification schemes genome organization

  • A. Formal taxonomies

  • B. Baltimore Classification


C nucleic acid type baltimore classification
C. Nucleic acid type --> Baltimore classification genome organization

  • Class I

    • ds DNA

  • Class II

    • ssDNA (positive and negative)

  • Class III

    • dsRNA

  • Class IV

    • ssRNA (positive)


  • Class V genome organization

    • ssRNA (negative)

  • Class VI

    • ssRNA (positive, replication intermediate DNA)


1 class i dsdna viruses
1. Class I: dsDNA Viruses genome organization

  • Bacterial

    • Bacteriophage

  • Plant

    • Caulomoviridae


  • Human genome organization

    • Herpesviridae

    • Adenoviridae

    • Poxviridae

    • Papovaviridae

      • Papillomavirus

      • Polyomavirus

      • Vacuolating agent


  • Hepadnaviridae genome organization

    • After protein synthesis, DNA replicated through RNA intermediate


2 class ii ssdna viruses
2. Class II: ssDNA viruses genome organization

  • Bacteria

  • Plant

  • Animal


3 class iii dsrna viruses
3. Class III: dsRNA viruses genome organization

  • Reoviridae


4 class iv ss rna viruses
4. Class IV: ss (+) RNA viruses genome organization

  • Picornaviridae

  • Togaviridae

  • Flaviviridae

  • Coronaviridae

  • Calciviridae


5 class v ss rna viruses
5. Class V: ss (-) RNA viruses genome organization

  • Rhabdoviridae

  • Filoviridae

  • Paramyxoviridae

  • Orthomyxoviridae

  • Bunyaviridae

  • Deltaviridae

  • Arenaviridae



6 class vi ss viruses dsdna intermediate
6. Class VI: ss (+) viruses (dsDNA intermediate) genome organization

  • Retroviridae

    • Oncoviruses

    • Lentivirus




Viii oncogenic viruses
VIII. Oncogenic Viruses genome organization


Ix plant viruses
IX. Plant viruses genome organization

  • Morphologically similar to animal viruses

  • Enter through wounds or parasites

  • Some multiply in insects


X viroids
X. Viroids genome organization

  • Plant pathogens

    • infectious naked RNA

  • 20-25 identified so far

  • ss covalent circle


Xi prions
XI. Prions genome organization

  • A. Fig 13.21

  • B. PrPC vs PrPSc

    • Structural differences

    • Detergent solubility differences

    • Differences in susceptibility to protein degrading enzymes



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