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Transcript
Viruses Viruses are not a type of bacteria! Virus comes from the Latin word for poison. Viruses are so small they can only be seen with Electron Microscope. Bacteria and other cells are large enough to be seen with a light microscope. Not considered to be a living thing because they are non-cellular particle. They are only made up of genetic material (DNA or RNA) and a protein coat. Parasites! CANNOT carry out life processes unless within a host (living cell). Usually host specific- infect only one type of host. Figure 19-13 Virus Structures Viruses infect a variety of different organisms and come Section 19-3 in many different shapes Tobacco Mosaic Virus T4 Bacteriophage Protein Influenza Virus RNA DNA RNA Protein Protein Tail Tail fiber Surface proteins Infects: plants Infects: bacteria Go to Section: Envelope Infects: Animals Viral Diseases Mostly caused by virus destroying cells in body. Cause human diseases such as polio, measles, AIDS, and the common cold Viruses are generally destructive. Virus has to be inside a living cell to reproduce. The cell that it reproduces in is a host cell. A virus destroys its host cell. Lytic Cycle -how a virus reproduces When a virus enters a cell and is active it causes the cell to make new viruses. This will eventually destroy the host cell. Steps of Lytic Cycle 1. Attach-virus attaches to the surface of a cell 2. Inject- the hereditary material of the virus injects itself into the cell. 3. Copy-the viral DNA takes control of the cell and the cell begins to make new virus particles. 4. Assembles- viral particle are assembled into new viruses 5. Release-the cell bursts open and hundreds of new virus particles are released. These new virus particles go on to infect other cells. Figure 19-14 The Lytic Cycle Attach Section 19-3 Bacteriophage Release DNA Bacterial DNA Lytic Cycle Inject Assemble Bacteriophage Copy Go to Section: Bacteriophage DNA Bacteriophage protein Latent Viruses- (Dormant Virus) Do not immediately enter the lytic cycle. The viral DNA becomes part of the cell’s DNA without immediately destroying the cell or making new viruses. A latent virus can exist inside host cells for many years. Can become active at any time. Ex- Cold sores. Viral Diseases CANNOT be treated with antibiotics Best Protection is prevention - Prevented by safe practices or Vaccine if available. (Vaccines must be used before infection begins) Franklin D Roosevelt Rabies SARS- flu-like virus that leads to severe pneumonia Ebola virus- liquification of internal organs and severe bleed out III. Kinds of Viruses A. Viruses are classified by their shape, the kind of hereditary material they contain, organism that they infect and reproduction. B. The protein that covers a virus gives it its shape. C. Viruses are often named for the disease that they cause (Polio) or the organ or tissue that they infect (SARS). VII. Steps of Lysogenic cycle 1. Virus attaches to the cell and injects hereditary material into the cell. 2. Virus becomes part of the cell’s DNA. 3. Cell divides, creating viral DNA along with its own DNA. 4. This can happen for years until virus becomes active 5. Then it will enter the lytic cycle Figure 19-15 A Lysogenic Infection Section 19-3 a) Virus attaches and invades Bacterial chromosome Bacteriophage DNA c) Viral DNA separates from Cell’s DNA and becomes active c) Cell divides Lytic Cycle e) Cell breaks open and Releases virus Prophage d) New viruses are made Go to Section: Lysogenic Cycle b) Virus’ DNA becomes Part of Cell’s DNA Bovine Spongiform Encephalopathy Mad Cow Disease VIII. Prions- no genetic material (DNA nor RNA) only protein which infects the nervous tissue of the brain (scientists think they cause Mad Cow Disease). Finding the host: Outbreak!