- Scientist: Frederick Griffith.
- Experiment:
1. He worked on \(\textit{Streptococcus pneumoniae}\) (S strain = virulent, R strain = non-virulent).
2. Heat-killed S strain mixed with live R strain transformed R into a virulent S strain.
- Conclusion:
- A "transforming principle" (later identified as DNA) is responsible for genetic stability and transfer of traits.