Thomas J. King Jr.

Thomas Joseph King Jr. (1921-2000) was an American embryologist and cancer researcher who, with colleague Robert Briggs at the Institute for Cancer Research in Philadelphia, developed the technique of nuclear transplantation that underlies modern cloning. Born in New York City, he earned a bachelor's degree from Fordham University in 1943 and trained in microsurgery before joining Briggs as a research fellow in 1950. In 1952 the two scientists removed the nucleus from a frog egg and replaced it with a donor nucleus taken from a blastula-stage embryonic cell, and showed the resulting eggs could develop into viable tadpoles, the first successful nuclear transplantation performed in a multicellular animal. King later used the same transplantation method in cancer research, showing that nuclei from certain cancer cells could still direct normal embryonic development, evidence that challenged assumptions about how cancer cells differentiate. He went on to hold research and leadership positions at Georgetown University and the National Cancer Institute before retiring in 1990.