Smith, Hamilton O

Smith, Hamilton O(thanel)

(born Aug. 23, 1931, New York, N.Y., U.S.) U.S. microbiologist. He received his M.D. from Johns Hopkins University. While studying the mechanism whereby the bacterium Haemophilus influenzae takes up DNA from a particular bacteriophage, Smith, Werner Arber, and Daniel Nathans discovered the first of what came to be called type II restriction enzymes. Whereas previously studied restriction enzymes cut DNA at unpredictable points, the type II enzymes' predictability allowed the scientists to cut DNA at a particular point. The enzymes have become valuable tools in the study of DNA structure and in recombinant DNA technology. The three shared a 1978 Nobel Prize.