Viruses - PowerPoint PPT Presentation

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  1. Viruses Alive or not?

  2. There are many viruses that affect humans. Here are a few of them. The AIDS Virus

  3. Herpes simplex virus

  4. Smallpox virus

  5. Different types of Influenza viruses

  6. Measles virus

  7. Ebola Virus

  8. Viruses attack specific species and often specific cells.A virus that would affect a human would not affect different organism. Bacteriaphage viruses attack only bacteria Tobacco Mosiac virus Attacks tobacco plants

  9. Human Skin Cell Viruses Bacteria Viruses remained undiscovered for so long because they are very small.

  10. The very first virus discovered on the 12th February 1892 by Dmitri Iwanowsk (1864-1920), a Russian botanist. While studying mosiac tobacco disease, he found that the agent causing the disease was small enough for pass though ceramic filter that are small enough to trap all bacteria. This is generally accepted as the beginning of Virology.

  11. So what is a virus? The virus is made up of 2 basic structures: 1. A core of DNA or RNA 2. A protein coat surrounding the DNA or RNA called a capsid Sometimes they have tail fibers that help them attach to a host cell.

  12. Viral reproduction is quite fascinating! 1. The virus attaches to the membrane of a host cell.

  13. 2. The virus injects its genetic material into the host cell.

  14. The viral DNA is replicated by the host • cell.

  15. 4. The viral DNA and protein coats are produced by the host cell.

  16. 5. The parts of the virus assemble

  17. 6. Viral enzymes break down the membrane causing the host cell to split open. Now the new viruses infect neighboring cells.

  18. So how can you fight a viral infection? There are no medications or drugs that can help you get rid of a virus. Antibodies are produced in the blood (yellow) which are specific to the attacking virus (green) The antibodies disable the virus but only after you have felt the affects of the illness

  19. Prevention of Viruses • Viral infections can be prevented with a vaccine. • A vaccine is a liquid that contains a weakened form of the virus (usually the protein coat) • This fools the body into producing antibodies so that when the real virus attacks, the body is ready to disable it.

  20. Types of Vaccinations you have received. • Tetanus • Influenza • Polio • Mumps • Measles • Rubella • Chicken pox • Hepatitis

  21. How to avoid getting and spreading the flu virus Wash your hands often Get plenty Of rest Drink lots of water Get a flu shot Avoid sick people Don’t eat at buffets  Eat healthy foods Like fruits and vegetables

  22. How do viruses and cells compare? Reproduction: Viruses- only reproduce with a host cell Cell- independent cell division Genetic Code: Virus- DNA or RNA Cell- DNA Growth and Development: Virus- no Cell- yes, cells increase in size and number

  23. Obtain and Use Energy: Virus- no Cell- yes Respond to the environment:Virus- no Cell- yes Change over time: Virus- yes Cell- yes

  24. What do you think? Are viruses alive? Give evidence to support this opinion: YES NO