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Mohamed Nasreldin

History of DNA. 1. Mohamed Nasreldin. “Transforming Factor”. In 1928, Fredrick Griffith, a British Biologist, did an experiment on mice He injected two strains of bacteria into the mice One was harmful, the other was harmless. 2. “Transforming Factor”.

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Mohamed Nasreldin

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  1. History of DNA 1 Mohamed Nasreldin

  2. “Transforming Factor” In 1928, Fredrick Griffith, a British Biologist, did an experiment on mice He injected two strains of bacteria into the mice One was harmful, the other was harmless 2

  3. “Transforming Factor” He injected Strain 1 (harmful) into the first mouse, it died The second mouse, he injected Strain 2 (Harmless), it survived The third mouse, He injected a heat treated Strain 1, the mouse survived In the fourth mouse he injected a mixture of strain 2 and heat treated strain 1, the mouse died. 3

  4. “Transforming Factor” 4

  5. “Transforming Factor” Since the fourth mouse died, Griffith concluded that there was a transforming factor. The harmless strain transformed and became deadly. 5

  6. Oswald Avery American Biologist Took Griffith’s experiments a step further Wanted to find out what was the transforming factor. Thought it might be Protein 6

  7. Avery’s Experiments Treated Griffith’s mixture of heat-treated deadly strain and live harmless strain with protein-destroying enzymes The bacteria grown from the mixture was still transformed He concluded that Protein was not the transforming factor 7

  8. Avery’s Experiments He then treated the mixture with DNA destroying enzymes The bacteria colonies did not transform Avery concluded that DNA is the genetic material 8

  9. Further Experiments Many scientists did not believe Avery Still believed Protein was the “transforming factor”because DNA was too simple Further research had to be conducted 9

  10. Hershey and Chase Wanted to make sure the transforming factor was DNA Used viruses for testing 10

  11. Hershey and Chase Knew that the phage had two components - DNA and Protein They were not sure which one had the hereditary material Made an experiment to determine which part of the phage it was DNA or the protein 11

  12. Hershey and Chase For one batch, they used a radioactive isotope of sulfur(found only in Protein) The other batch they used a radioactive isotope of phosphorus(found in DNA) 12

  13. Hershey and Chase They concluded that DNA was the hereditary material Their experiment convinced other scientists that DNA contains the genetic material 13

  14. Hershey and Chase When the protein coats were labeled, the radioactivity was detected outside the cells When DNA coats were labeled, the radioactivity was detected inside the cells 14

  15. Bibliography http://edu.glogster.com/media/4/14/58/61/14586124.jpg http://www.csb.yale.edu/userguides/graphics/ribbons/help/dna_rgb.gif http://www.mun.ca/biology/scarr/Chase_&_Hershey_1953.jpg 15

  16. The END 16

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