Chapter 6 - Viruses

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Chapter 6 - Viruses

• Obligate Intracellular Parasites only
  demonstrate characteristics of life while
  inside a host cell Bacteria, animal, plant

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Chapter 6 - Viruses

• Outside a host cell, inert, no enzyme or other
  activity
• Inside a host cell viral Nucleic Acid (DNA or
  RNA) takes over the cell and directs the cell to
  produce new virus particles (replication)
• Size of Viruses See page in text 155?, very
  tiny (picorna) to huge (pox viruses)

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Chapter 6 - Viruses

• Basic virus particle is called a virion
  intact and infective virus particle
• Components Nucleic Acid (DNA or RNA), Protein
  coat (capsid) made of individual protein subunits
  called capsomeres. Some may have and outer
  envelope, a membrane, derived from the host cell.
  The envelope can have specific spikes of protein
  (H and N spikes of Influenza) that aid in
  attachment and makes them sensitive to chemical
  actions of disinfectants.

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Chapter 6 - Viruses

• Types of viruses based on morphology shape
  structure
• Helical (like TMV or Ebola) Polyhedral (adeno
  and polio) Enveloped (flu) and Complex
  (bacteriophage)

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Chapter 6 - Viruses

• EBOLA

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Chapter 6 - Viruses

• Polio virions

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Chapter 6 - Viruses

• Influenza A Enveloped, with spikes, RNA,
  multisegmented genome (8 separate pieces of RNA)

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Chapter 6 - Viruses

• Bacteriophage Complex

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Chapter 6 - Viruses

• Taxonomy of viruses complicated and boring
  well leave it to the ones with a higher
  paygrade

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Chapter 6 - Viruses

• Cultivation of viruses need living cells,
  living hosts
• Tissue cultures, embryonated eggs, bacterial
  cultures

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Chapter 6 - Viruses

• Cultivation of viruses need living cells,
  living hosts
• Tissue cultures, embryonated eggs, bacterial
  cultures
• Bacteria grown as a lawn and viruses are in
  the clear zones, plaques

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Chapter 6 Viruses Viral replication in
bacteria life cycle of bacterial virusLYTIC
Cycle
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Chapter 6 - Viruses

• Viral replication in bacteria life cycle of
  bacterial virus
• Lysogneic (latent) cycle, genome of virus
  incorporated into host cell genome infected with
  seeds of destruction

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Chapter 6 - Viruses

• Animal Virus Life Cycle Penetration, Uncoating,
  Biosynthesis, Assembly, Maturation, Release Can
  have Latent infection also.

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Chapter 6 - Viruses

• Animal Virus Life Cycle Penetration, Uncoating,
  Biosynthesis, Assembly, Maturation, Release Can
  have Latent infection also. Latent infection is
  seen in herpes type and even HIV

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Chapter 6 - Viruses

• Animal Virus Life Cycle Penetration, Uncoating,
  Biosynthesis, Assembly, Maturation, Release Can
  have Latent infection also. Latent infection is
  seen in herpes type and even HIV
• Hiv is a RNA virus, a retrovirus with an enzyme
  called reverse transcriptase causes DNA to be
  synthesized from genome that is RNA (backwards)
  The Drug AZT works on HIV by inhibiting this
  enzyme

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Chapter 6 - Viruses

• Budding of an animal virus from a host cell

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Chapter 6 - Viruses

• Budding of rabies viruses electron
  photomicrograph

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Chapter 6 - Viruses

• Multi-segmented RNA genome of Influenza higher
  mutation rate, genetic shift and drift, new
  vaccines required

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Chapter 6 - Viruses

• Prions Infectious proteins, cause scrappie in
  sheep, Kuru in humans, BSE in cattle, and KJD in
  people (mad cow in humans)
• Watch the video The Brain Eaters Spoingioform
  encephalopathy

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