Avery, MacLeod, and McCarty's landmark study followed up on the work of Griffith (diagrammed below).

1. Purified S strain extracts to characterize the transforming principle.

2. Material was resistant to proteases; it contained no lipid or carbohydrate.

3. If DNA in the extract is destroyed, the transforming principle is lost.

4. Pure DNA isolated from the S strain extract transforms R strain.

5. Avery cautiously suggested that DNA was the genetic material.

6. This was the first experimental evidence that DNA is the genetic material.