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Chapter Viruses Ch 19

Get a half sheet of paper out, number 1-5. You are taking an assessment on the disease gizmo from yesterday. Chapter Viruses Ch 19. Viruses. Characteristics of Viruses 1. Tiny, nonliving particles a. do not respire, move, grow

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Chapter Viruses Ch 19

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  1. Get a half sheet of paper out, number 1-5. You are taking an assessment on the disease gizmo from yesterday

  2. Chapter Viruses Ch 19 Viruses

  3. Characteristics of Viruses 1. Tiny, nonliving particles a. do not respire, move, grow 2. Must reproduce inside of a host 3. Pathogens: disease-causing a. Virulence: degree of response caused in a host 4. Not given latin names a. named for disease caused, organ infected, or region first detected in

  4. Viral Structure • Inner core of nucleic acid surrounded by protein coat called capsid a. head contains either DNA or RNA body

  5. RNA DNA Head RNA Capsid Capsid proteins Tail sheath Tail fiber Surface proteins Membrane envelope Figure 19-13 Virus Structures Section 19-3 Tobacco Mosaic Virus T4 Bacteriophage Influenza Virus Go to Section:

  6. Recognition & Attachment of Viruses 1. Virus must recognize specific receptor site on host. A. part of the virus matches site on host B. lands on host and “locks in”

  7. 2. Attachment is specific a. virus can enter & reproduce in only a few kinds of cells Example: tobacco mosaic virus cannot affect human cells even though we are exposed to it.

  8. There are 2 ways viruses can reproduce inside a host. • Lytic cycle-fast • Lysogenic cycle-slow

  9. Lysogenic Cycle( virus can enter a period of inactivity before becoming lytic) STEPS 1. Attachment- virus attaches to the host cell 2. Entry- whole virus or just nucleic acid enters the cell 3. Replication- viral nucleic acid joins w/DNA of host cell. It may stay there inactive for years. Host cell continues to divide

  10. If the cell reproduces, the viral nucleic acid is also copied so each new cell is infected. 4. the virus becomes active and enters the lytic cycle. 5. Assembly,lysis, & release- new viral nucleic acids & protein coats are assembled. The virus exits the host cell. Example- AIDS, Herpes

  11. Figure 19-15 A Lysogenic Infection Section 19-3 Bacterial chromosome Bacteriophage DNA Bacteriophage injects DNA into bacterium Bacteriophage DNA (prophage) can exit the bacterial chromosome Lytic Cycle Lysogenic Cycle Bacteriophage DNA (prophage) may replicate with bacterium for many generations Bacteriophage DNA forms a circle Bacteriophage enzyme lyses the bacterium’s cell wall, releasing new bacteriophage particles that can attack other cells Prophage Bacteriophage proteins and nucleic acids assemble into complete bacteriophage particles Bacteriophage DNA inserts itself into bacterial chromosome Go to Section:

  12. Common Diseases Caused by Viruses Section 19-3 Type of Virus Nucleic Acid Disease Oncogenic viruses Retroviruses Adenoviruses Herpesviruses Poxviruses DNA RNA DNA DNA DNA cancer cancer, AIDS respiratory infections chickenpox smallpox Go to Section:

  13. Go to Section:

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