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History of DNA-Discovery and Structure Feb. 20, 2009 Frederick Griffith • 1928 • British • Isolated two slightly different strains of pneumonia bacteria from mice, experimented, and discovered transfomation. Griffith- Experiment Griffith-Experiment • What does this mean? – Transformation of non-deadly strain by heatkilled deadly strain. – This told Griffith that some type of information could be passed between two different strains. – Hypothesized that genes were passed. Beadle and Tatum • 1941 • Used radiation and bread mold to investigate enzymes (proteins). • Determined the “one gene, one enzyme” relationship. Beadle and Tatum-Experiment Beadle and Tatum-Experiment • What does this mean? – By changing a single gene in the mold, a single enzyme was changed. – Each gene codes for an enzyme- one gene, one enzyme. Avery • 1944 • Canadian • Repeated Griffith’s work. • Wanted to know what molecule was being transferred to cause the transformation. • Discovered that DNA stores and carries genetic information from one generation to another. • No one believed him. Avery-Experiment Griffith Avery Avery-Experiment • What does this mean? – When proteins in the deadly strain were destroyed the cell could still transform the non-deadly strain mouse died, not protein passing genetic information. – When DNA in the deadly strain was destroyed the cell could not transform the non-deadly strain mouse lives, DNA passes genetic information. Hershey and Chase • 1952 • American • Used radioactive bacteriophages (virus that kill bacteria) to determine what molecule was carrying the genetic material. • Determined that the genetic material in the bacteriophage was DNA, not protein. Hershey-Chase-Experiment Hershey-Chase-Experiment • What does this mean? – When protein was followed from the virus to the bacteria, it stayed with the virus not being passed on as genetic material. – When DNA was followed from the virus to the bacteria, it ended up in the bacteria passed on as genetic material. – It is DNA that contains the genetic code. Homework-Due Feb. 23! • Create a timeline showing when Mendel, Griffith, Beadle, Tatum, Avery, Hershey, and Chase worked. • Include a brief description of each experiment and what the experiment proved. • Include at least two pictures/diagrams. • The timeline should be at least the length of two pieces of paper (about 22 inches). • Any extra effort will be rewarded.