Transformation efficiency of bacteria (as in the experiment of Avery et al) would be drastically reduced if the transforming material is treated with

Oswald Avery, Colin Mac Leod and Maclyn McCarty worked to determine the biochemical nature of transforming principle in Griffith’s experiment, it was DNA that was the transforming principle that was transferred from S-strain to R-strain, hence the transformation is regarded as the first undoubted evidence that DNA is the genetic material.