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VIRUSES

VIRUSES. What is a VIRUS?. Viruses are small infectious agents They are so small that they can only be seen with a very powerful electron microscope. Swine Flu Virus under electron microscope. Ebola Virus under electron microscope. What is a VIRUS?.

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VIRUSES

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  1. VIRUSES

  2. What is a VIRUS? • Viruses are small infectious agents • They are so small that they can only be seen with a very powerful electron microscope Swine Flu Virus under electron microscope Ebola Virus under electron microscope

  3. What is a VIRUS? • Viruses are highly specific to the cells they infect • Viruses that infect bacteria are called bacteriophages • A retrovirus is a virus that contains RNA rather than DNA • A virus can reproduce only by infecting living cells; Once they infect a cell, they use that cell’s “materials” to produce more viruses

  4. Parts of a Virus • A typical virus is composed of a core of DNA or RNA (nucleic acids) surrounded by a protein coat (capsid) • Viruses come in a wide variety of shapes and sizes • The capsid contains proteins that allow a virus to bind to a cell and “trick” the cell into allowing it inside

  5. DNA or RNA Capsid BODY

  6. Check for Understanding • With your partner, explain whether a virus is living or non-living (think back to the characteristics of life). • Time: 1 minute

  7. Living or Non-Living? • Viruses are considered NON-LIVING • WHY? • They are not made up of cells • They are not capable of living independently (require a host cell) • They do not grow and develop • They do not obtain and use energy • They do not respond to their environment

  8. Viral Infection

  9. Viral Infection/Reproduction • Once a virus is INSIDE the host cell, two different things can occur • LYTIC INFECTION: The virus immediately makes copies of itself and causes the cell to burst (releasing the replicated viruses) • LYSOGENIC INFECTION: The virus intertwines its DNA with the host DNA, but lies dormant for a period of time. In a sense it “hides out” until it is ready to enter the lytic stage

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