MCCARTY, MACLYN

(b. June 9, 1911, South Bend, Ind., U.S.), American biologist who, with Oswald T. Avery and Colin M. MacLeod, provided the first experimental evidence that the genetic material of living cells is composed of deoxyribonucleic acid (DNA). McCarty attended Stanford University and Johns Hopkins School of Medicine (M.D., 1937) before joining William S. Tillett at New York University in 1940. Tillett not only introduced McCarty to the study of pneumococcic bacteria but also arranged for him to work with Avery in his laboratory at the Rockefeller Institute (now Rockefeller University), New York City. McCarty became a member of the institute in 1950 and, 15 years later, its vice president and physician in chief. McCarty's classic experiments with Avery and MacLeod, published in 1944, involved the transformation of certain types of pneumococcus into distinctly different types. The transformation occurred when cell-free material, extracted from one type of bacterium encased in smooth capsules in the living state, was mixed with living bacteria of a second type lacking capsules. The second type would then produce a capsule characteristic of the first type, with which it had been mixed. The results of this research indicated that the substance responsible for the change was DNA.