Viruses

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Viruses

• What is a virus?
• non living particles of nucleic acid, protein
  and in some case lipids
• Can reproduce by infecting host cell

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Composition

• Core composed of DNA or RNA
• Capsidouter coat or protein coat
• Envelope- another protective covering found on
  some viruses made of lipids taken from a host

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Characteristics of Viruses

• Reproduction- only occurs with a host cell
• smallest particle which can cause disease
• composed of compounds found in cells
• Contain no
• cytoplasm
• nucleus
• organelles

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Viral Infections

• Viruses are specific to the cells they infect
• 2 types
• Lytic Infection
• Virus enters a cell, Makes copies of itself
• Causes cell to burst
• Begins with mRNA from virus
• Lysogenic Infection
• Host cell makes copies of virus indefinitely
• Viral DNA embeds into host DNA

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Artistic rendition of the Lytic Cycle
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The Lysogenic Cycle temperate virus
Host cells are not immediately killed, the host
cells replicate and in this process copy the
viral genome
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Retroviruses

• Retroviruses?viruses that contain RNA as their
  genetic information
• Makes DNA copy of their RNA
• Causes HIV