Virus Introduction - PowerPoint PPT Presentation

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  1. Virus Introduction

  2. What is a Virus? • A small infectious agent that can replicate only inside the cells of other organisms, bacteria, plants or animals. • Consists of at least two of three parts • Genetic material, DNA or RNA (retro virus) • Protein coat that protects the genetic material • Possible lipid membrane

  3. How do they compare to Bacteria? • They both can cause disease and have a similar structure

  4. Are viruses alive? • Viruses have characteristics that may classify them as living. • They also have characteristics that classify them as non-living • They have no metabolism and cannot reproduce on their own so they do not qualify as a living organism.

  5. How small are viruses? • Viruses are typically 20 – 400 nm • Bacteria are typically 1000 nm

  6. 4Shapes of a virus • Helical

  7. Icosahedral

  8. Envelope

  9. Complex

  10. Virus discovery and origin • In 1884 by French microbiologist Charles Chamberland • Origin is unclear because they do not leave behind any fossils or life evidence • The viruses that have been preserved by scientists date back about 90 years • There are 3 different theories of possible origin

  11. 1. Regressive • Viruses may have been small cells that parasitized larger cells and then lost unnecessary genes • 2. Cellular • May have evolved from bits of DNA, RNA or plasmids that may have escaped or been lost • 3. Coevolution • May have evolved from complex proteins and genetic material at the same time as cells first originated and are dependant on cells to stay in existence