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Chapter 10B

Chapter 10B. Viruses. The Discovery of Viruses. Iwanowski (1892) Tobacco mosaic Virus: Latin for “poison” Stanley (1930s) Won a Nobel Prize for isolating TMV. What Is a Virus?. More than just a chemical Capable of replication Noncellular, but contains DNA or RNA. CONTROVERSY.

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Chapter 10B

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  1. Chapter 10B Viruses

  2. The Discovery of Viruses • Iwanowski (1892) • Tobacco mosaic • Virus: Latin for “poison” • Stanley (1930s) • Won a Nobel Prize for isolating TMV

  3. What Is a Virus? • More than just a chemical • Capable of replication • Noncellular, but contains DNA or RNA

  4. CONTROVERSY Are viruses living or nonliving?

  5. The Structure of Viruses

  6. Virus Structure • Molecule of DNA or RNA (the core) and a protein coat (the capsid) • Lipid envelope • Complete virus = virion • No plasma membrane, cytoplasm, or organelles

  7. Viroids and Prions • Viroid: a short, single strand of circular RNA • Prion: an abnormal form of a protein • Smaller than viruses • Thought to cause some diseases

  8. Viral Replication • Obligate intracellular parasites • Bacteriophage: a virus that infects certain bacteria

  9. Virulence • The ability of a pathogen to affect cells

  10. Lytic Cycle • The activity of a virulent virus

  11. Steps of the Lytic Cycle • Attachment • Entry • Replication and transcription • Assembly • Release

  12. The Lysogenic Cycle • Latent virus: a virus that enters a cell and remains inactive for a period of time • During this time, the virus is replicating.

  13. Other Kinds of Viruses • Persistent infections—slowly release virusparticles without goingthrough the lytic cycle • Transforming viruses—add new genetic information to the host cell

  14. Viral Diseases

  15. Viruses are . . . • highly specific. • limited to certain types of organisms or cells. • hard to destroy once they are inside a cell.

  16. Control of Viral Diseases • Vaccination • Activates the body’s immune system to recognize and fight pathogens • Inactivated • Attenuated

  17. Control of Viral Diseases • Antiviral drugs • Interferons • Chemicals produced by the body as a defense against viruses

  18. Viruses are . . . • continuing to emerge.

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