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In the 1920's, a scientist named Frederick Griffith was researching how bacteria caused disease when he discovered transformation.
Griffith mixed heat-killed, disease causing bacteria with live, non-disease causing bacteria. This resulted in the non-disease causing bacteria to change into disease causing bacteria. An unknown "factor" was causing this change. Griffith's discovery prompted more scientists to search for the "factor" in transformation eventually leading to the discovery of DNA.
Textbook Link: Go to page 288; DNA 12-1
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