Discovery of DNA as the Hereditary Material

In a 1944 paper, the researchers Oswald Avery, Colin MacLeod, and Maclyn McCarty showed that a purified sample of DNA on its own could transform one strain of pneumococcus bacteria into another, heritable trait and all. Their result built on Frederick Griffith's 1928 discovery of what he called a transforming principle passed between bacteria, but Avery, MacLeod, and McCarty were the first to identify that principle chemically as DNA rather than the protein that most scientists of the time had assumed must carry hereditary information. Their finding is regarded as the foundational experiment establishing DNA, rather than protein, as the molecule of heredity, opening the path that led within a decade to the discovery of DNA's structure.