R cells+ purified s cell polysaccharide R colonies R cells purified S cell protein R colonies R cells purified s cell RNA R colonies R cells purified S cell DNA S colonies S cell extract protease +R cells S colonies S cell extract + RNase +R cells S colonies Figure 11. 2 Experiments on the Transforming Principle. Summary of the experiments of Avery, MacLeod, and McCarty on the transforming principle. DNA alone changed R to S cells, and this effect was lost when the extract was treated with deoxyribonuclease. Thus DNA carried the genetic information required for the R to S conversion or transformation