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The Biology of Viruses

The Biology of Viruses. Where do viruses fit in the 3 domain, 6 kingdom classification of life?. Viruses do not fit into the classification of life because they are not considered to be living things Not composed of cells Cannot reproduce on their own. Properties of Viruses.

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The Biology of Viruses

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  1. The Biology of Viruses

  2. Where do viruses fit in the 3 domain, 6 kingdom classification of life? • Viruses do not fit into the classification of life because they are not considered to be living things • Not composed of cells • Cannot reproduce on their own

  3. Properties of Viruses • 1. Extremely Small • 2. Simple • A) nucleic acid core surrounded by: • B) outer protective protein coat called a capsid

  4. The Structure of Viruses Tobacco Mosaic Virus HIV Bacteriophage

  5. Properties of Viruses • 1. Extremely Small • 2. Simple • A) nucleic acid core surrounded by: • B) outer protective protein coat called a capsid • 3. Contain DNA or RNA • 4. Genetic material may be single or double-stranded

  6. Viral Reproduction • Viruses have a very simple function: invade a host cell and start reproducing • Each virus infects only a limited number of host cells, this is called its host range • Viruses identify their hosts by a “lock and key” fit between proteins on the outside of the virus and receptor molecules on the surface of the host • A virus which infects and destroys bacterial cells is a bacteriophage

  7. Viral Replication • Read and summarize the 4 steps of viral replication on page 336 • What is a virulent phage? • What is a temperate phage? How does replication in a temperate phage differ from replication in a virulent phage?

  8. Viral Replication • What is a virulent phage? • A virus which causes lysis (death) of the cell it invades • What is a temperate phage? How does replication in a temperate phage differ from replication in a virulent phage? • A virus whose DNA becomes integrated into its host cell and passed on to the host’s daughter cells • These viruses do not destroy the cells they infect unless they enter the lytic cycle

  9. Lytic vs Lysogenic Cycles

  10. Viral Infections • Common cold, influenza, herpes, HIV • Prevention: • Vaccines containing inactivated viruses will artificially trigger an immune response • Body produces antibodies against the virus • Treatment: • Antiviral medications are designed to interfere with viral replication or strengthen the body’s immune response against the virus

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