Hamilton O. Smith Biography (1931-)

molecular biologist

Hamilton Othanel Smith shared the 1978 Nobel Prize in physiology or medicinewith fellow biologists Werner Arber and Daniel Nathans for the set of linkeddiscoveries that started off the boom in biotechnology. Because of these discoveries, researchers can more easily elucidate the structure and coding of deoxyribonucleic acid (DNA) molecules (the basic genetic map of an organism), and they hope to correct many genetic illnesses in the future. His research also made it possible to design new organisms, a controversial but potentiallybeneficial technology. Smith purified and explained the activity of the firstrestriction enzyme, which became the principal tool used by genetic engineers to selectively cut up DNA. (Arber had linked restriction and modification to DNA, and predicted the existence of restriction enzymes. Nathans, under Smith's encouragement at Johns Hopkins, developed techniques that enabled theirpractical use.)

Smith was born on August 23, 1931, in New York, New York, to Bunnie (Othanel)Smith and Tommie Harkey Smith. Smith graduated from University High School in three years, enrolling at a local university in 1948.

Smith came to the study of genetics by way of medicine. Initially a mathematics major at the University of Illinois, he transferred to the University of California at Berkeley in 1950 to study biology and graduated with a bachelor's degree in 1952. He obtained a medical degree from the Johns Hopkins Schoolof Medicine in 1956. During the years 1956 to 1962, he held various posts, including an internship at Washington University in St. Louis, Missouri, a two-year Navy stint in San Diego, California, and a residency at Henry Ford Hospital in Detroit, Michigan. He gradually taught himself genetics and molecularbiology in his spare time. In 1962 he began a research career at the University of Michigan on a postdoctoral fellowship from the National Institutes of Health, before finally returning to Johns Hopkins in 1965 as a research associate in the microbiology department. He was named a full professor of microbiology in 1973, and professor of molecular biology and genetics in 1981. In 1975, Smith was awarded a Guggenheim Fellowship for a year of study at the University of Zurich in Switzerland.

After his return to the United States, Smith purified the first Type II restriction endonuclease, which he obtained from the bacterium Hemophilus influenzae, and identified the nucleotide sequence which the enzyme would cut. He gave a supply of the enzyme to Daniel Nathans, who used it in his own work. The three men eventually won the 1978 Nobel Prize. The presenter of the prize noted that Smith proved Arbor's hypothesis about restriction enzymes, pointing the way for future research.

Smith's exacting specificity of Class II restriction enzymes makes them useful because biotechnologists can now cut DNA apart selectively. Then they can add and subtract specific nucleotides, and reproducibly weld (recombine) the links back together in a new order. This new piece of DNA now codes for a different protein. The current and potential uses of these procedures are enormous. Biotechnologists can genetically engineer bacteria that produce a particular chemical; human insulin for the treatment of diabetes is now made by suchrecombinant bacteria. Other bacteria have been designed to clean up oil slicks. One of the tasks that biotechnologists would like to accomplish is the eradication of genetic illness by correcting the mistaken DNA codes that cause it.

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