1. The Hunt for Fame Fortune and DNA Chapter 13.1 AP Biology Fall 2010

2. Early and Puzzling Clues Johann Miescher is credited with the discovery of DNA in the late 1800s

3. Early and Puzzling Clues In 1928, Fred Griffith was working with S (pathogenic) and R (nonpathogenic) strains of a pneumonia-causing bacterium Injected mice with R cells; mice lived Injected mice with S cells; mice died Blood samples contained many live S cells S cells were heat-killed, then injected into mice; mice lived Live R cells plus heat killed S cells were injected into mice; mice died Live S cells were found in blood

4. Griffith Experiments

5. Early and Puzzling Clues Some substance from the S cells had transformed the R cells Both proteins and nucleic acids were candidates In 1944, Oswald Avery showed the substance was DNA

6. Avery Experiments

7. Confirmation of DNA Function Viruses called bacteriophages use bacterial cells for reproduction Because they consist of only a protein coat and a nucleic acid core, these viruses were used in experiments by Hershey and Chase to prove which of these was the heredity material It was the nucleic acid

9. Confirmation of DNA Function 35 S labeled proteins in the bacteriophage coat did not enter the bacteria and thus were not participating in providing directions for new virus assembly 32 P labeled DNA in the viral core did not enter the bacteria and directed new virus assembly

10. Confirmation of DNA Function Linus Pauling deduced the structure and secrets of the protein collagen, bringing the biology community one step closer to DNA structural details

11. Enter Watson and Crick Watson and Crick used numerous sources of data to build various models of DNA In 1953, they discovered and published the structure of DNA