NIH History Office, https://www.flickr.com/people/124413887@N04 Restored by: Bammesk · Public domain

A biochemist who worked out how living cells actually copy their genetic material, isolating the enzyme — DNA polymerase — that assembles new DNA strands from a template. That discovery of the mechanisms behind nucleic acid synthesis, shared with Severo Ochoa, won the 1959 Nobel Prize in Physiology or Medicine and gave later generations of molecular biologists the enzymatic toolkit that made genetic engineering possible. He spent most of his career at Stanford, where two of his sons also became prominent biochemists.