Griffith's experiment

[3][4] Griffith's findings were followed by research in the late 1930s and early 40s that isolated DNA as the material that communicated this genetic information.

Pneumonia was a serious cause of death in the wake of the post-WWI Spanish influenza pandemic, and Griffith was studying the possibility of creating a vaccine.

Scientific advances since then have revealed that the "transforming principle" Griffith observed was the DNA of the III-s strain bacteria.

The III-S strain DNA contains the genes that form the smooth protective polysaccharide capsule.

The exact nature of the transforming principle (DNA) was verified in the experiments done by Avery, McLeod and McCarty and by Hershey and Chase.