Maclyn McCarty, Oswald Avery and the enzymatic evidence for DNA as the transforming substance

In Episode 8 of the DNA papers, we discuss the papers that directly followed up the discovery of the 1944 paper from episode 7. These papers, which have received little attention in histories of DNA, describe the purification and experimental use of an enzyme, desoxyribonuclease, or DNase, which specifically destroys DNA. By showing how the transforming principle is specifically inactivated by this enzyme alone and not by RNA- or protein-degrading enzymes- the DNase experiments left “little doubt” that DNA is the chemical substance responsible for the transformation of bacterial types.

Papers discussed include:

McCarty, Maclyn. 1946. “Purification and Properties of Desoxyribonuclease Isolated from Beef Pancreas.” The Journal of General Physiology 29 (3): 123–39.
McCarty, Maclyn, and O.T. Avery. 1946. “Studies on the Chemical Nature of the Substance Inducing Transformation of Pneumococcal Types. II. Effect of Desoxyribonuclease on the Biological Activity of the Transforming Substance.” Journal of Experimental Medicine 83: 89–96.

Returning to the podcast series to share their thoughts on the place of these experiments in DNA history are:

Mark Lorch, University of Hull
Geoffrey Montgomery, Independent Science Writer
Michel Morange, École Normale Supérieure
Jan Witkowski, Cold Spring Harbor Laboratory

Additional resources on this topic are available at https://www.chstm.org/video/144

Recorded on June 22, 2023.