Previous experiments in the 1920's revealed that a harmless strain of bacteria could become harmful by mixing the harmless bacteria with a lethal bacteria that had been already killed. what caused the change though was some kind of gene chemical. Oswald Avery through his experiments concluded that what actually transformed the gene though was in fact DNA,and not some protein that scientists originally thought. Oswald found this out by testing on mice. He first injected the live R bacteria into the mouse and it lived. Then, Oswald injected the second mouse with live S bacteria and the mouse died. Then, he injected just the dead S bacteria and the mouse lived. Finally, Oswald injected the mouse with the dead S bacteria and the live R bacteria. The mouse died concluding that the dead S bacteria had turned the harmless R bacteria into a lethal bacteria. Later, Oswald was able to isolate what caused the gene change which turned out to be DNA.
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