Jerry Donohue was an American chemist and crystallographer who worked in the Cavendish Laboratory. When Watson hypothesized that DNA’s two strands could have the same sequence of nitrogenous bases, Donohue pointed out that Watson’s model was based on the wrong molecular structures for guanine and thymine. Watson emphasizes his debt to Donohue—without whom Watson and Crick would have never discovered the double helix structure.