Final answer:
Frederick Griffith's experiments led to the discovery of the 'transforming principle,' later identified as DNA by Avery, McLeod, and McCarty, confirming it as the genetic material.
Step-by-step explanation:
Griffith's Discovery of the Transforming Principle
Frederick Griffith's landmark experiments in the 1920s were critical in leading to the discovery of DNA as the genetic material.
While studying Streptococcus pneumoniae, he observed the process of transformation, where the previously harmless R strain of bacteria became virulent after being mixed with heat-killed S strain bacteria.
The key question Griffith faced was identifying the substance responsible for this transformation, which he referred to as the 'transforming principle.'
It was not until the 1940s that Oswald Avery, Colin McLeod, and Maclyn McCarty built upon Griffith's work to demonstrate that DNA was the material responsible for transformation, thereby identifying it as the substance that carries genetic information.
Their work, along with later experiments by Hershey and Chase, conclusively showed that DNA, and not protein, was the molecule of heredity.
This series of discoveries underpinned the modern understanding of genetic inheritance and the role of DNA in biology.