feb 1, 1944 - Oswald Avery, Maclyn McCarty, Colin MacLeod
They studied heat killed S strands through many biochemical steps that purified the transforming principle by washing away, separating, or enzymatically destroying the other cell components. By the end of these steps, they obtained small amounts of purified transforming principle. They then figured out that this transforming principle is DNA, but then dismissed that conclusion after recognizing that there was probably small amounts of contaminants present.
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