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Discovery of DNA. Griffith ’ s Conclusion: “ something ” transformed the harmless bacteria into the deadly bacteria. (He called this process transformation) Oswald Avery – repeated Griffith ’ s work to determine which molecule was responsible for transformation
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Discovery of DNA Griffith’s Conclusion: “something” transformed the harmless bacteria into the deadly bacteria. (He called this process transformation) Oswald Avery – repeated Griffith’s work to determine which molecule was responsible for transformation • Conclusion: DNA was the transforming factor that caused the change in the R-strain
Discovery of DNA Alfred Hershey & Martha Chase • Question: Are genes made of DNA or proteins? • What they knew: • viruses use other organisms to reproduce • Viruses only contain DNA and a protein coat. • Whichever virus particle enters the cell must be the material that makes up genes (DNA).
Discovery of DNA Hershey and Chase • Experiment: • They tagged the virus DNA with blue radioactive phosphorous • They tagged the protein coat with red radioactive sulfur • Results: • the cells only contained blue radioactive phosphorous. • Conclusion: • Virus only injects DNA (confirms Avery’s results) http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120076/bio21.swf::Hershey%20and%20Chase%20Experiment