The proof that the material basis for a gene is DNA came from the work of Oswald T.Avery (1877-1955), Colin M. MacLeod (1909-1972), and Maclyn McCarty (1911-) in a paper published in 1944. This group of scientists followed the work of Griffith in order to discover what causes nonlethal bacteria to transform to a lethal strain. Using specific enzymes, all parts of the S (lethal) bacteria were degraded, including the sugar like coat, the proteins, and the RNA. The degradation of these substances by enzymes did not affect the transformation process. Finally, when the lethal bacteria were exposed to DNase, an enzyme that destroys DNA, all transformation activity ceased. The transforming factor was DNA.
