* Frederick Griffith (1928): He observed the phenomenon of transformation in bacteria. He showed that a harmless strain of bacteria could be transformed into a deadly strain by exposing it to heat-killed deadly bacteria. This suggested that some genetic material was transferred from the dead bacteria to the living ones.
* Oswald Avery, Colin MacLeod, and Maclyn McCarty (1944): They identified DNA as the transforming principle. They isolated and purified different components of the heat-killed bacteria (DNA, RNA, protein) and showed that only DNA was able to transform the harmless bacteria. This was a groundbreaking finding that definitively established DNA as the carrier of genetic information.
Therefore, while Griffith's initial observation of transformation was crucial, it was Avery, MacLeod, and McCarty who conclusively demonstrated that DNA is the molecule responsible for this process.
