Experiments by Avery, Macleod, and McCarty supported DNA as the genetic material by showing that:
(a) Both protein and DNA samples provided the transforming factor
(b) DNA was not complex enough to be the genetic material
(c) Only samples with DNA provided transforming activity
(d) Even though DNA was molecularly simple, it provided adequate variation to act as the genetic material
Avery, Macleod and McCarty purified biochemicals (proteins, DNA, RNA, etc.) from the heat-killed S cells to see which ones could transform live R cells into S cells. They discovered that DNA alone from S bacteria caused R bacteria to become transformed.
They concluded that DNA is the hereditary material.