Explain the role of the following scientists:
$1.$ Avery, MacLeod, and McCarty $(1933-44)$
$2.$ Matthew Meselson and Franklin Stahl $(1958)$

(N/A) $1.$ Oswald Avery, Colin MacLeod, and Maclyn McCarty $(1933-44)$: They worked to determine the biochemical nature of the 'transforming principle' in Griffith's experiment. They discovered that $DNA$ is the genetic material, not protein or $RNA$, by using enzymes like DNase, RNase, and protease.
$2.$ Matthew Meselson and Franklin Stahl $(1958)$: They performed an experiment using $E. coli$ grown in a medium containing $^{15}N$ (heavy nitrogen) and then transferred to $^{14}N$ (light nitrogen). Their results proved that $DNA$ replication is semi-conservative.