1931-

American molecular biologist who received the 1978 Nobel Prize for Physiology or Medicine, which he shared with Daniel Nathans and Werner Arber, for the discovery of restriction enzymes. Restriction enzymes are proteins that cut DNA chains and allow for modification of DNA molecules. This breakthrough opened up the field of biotechnology. Biotechnology companies now use hundreds of these restriction enzymes to make synthetic hormones and insulin, forming the basis for gene therapy, and for gene-mapping research, such as conducted by the Human Genome Project.