Question

Name the three scientists who followed up on Griffith’s experiments. What did they conclude and how?

Answer 1

Griffith’s experiments were followed by Oswald Avery, Colin MacLeod, and Maclyn McCarty (1933 - 44).

They concluded that DNA is the “transforming principle”, the chemical substance responsible for heredity. They reached this conclusion by chemically purifying different components (proteins, DNA, RNA, etc.) from the heat-killed S-strain bacteria. They then used specific digestive enzymes to see which one would prevent transformation:

• When they used proteases (to destroy proteins) and RNases (to destroy RNA), transformation still occurred; the R-strain still changed into the virulent S-strain.
• However, when they used DNases (to destroy DNA), transformation was completely inhibited.

This proved that neither protein nor RNA could carry the genetic information, but DNA was the molecule that permanently transformed the bacteria.