In 1912, the University of California, Berkeley, became the first university in the nation to form a separate Department of Genetics. The first two appointments in the department went to plant geneticists Ernest Brown Babcock and Roy E. Clausen, and as the department grew slowly, shifting slightly away from its roots in agricultural science, it gained a strong reputation as an important center for research in several areas in genetics and evolutionary biology. The U.C. Berkeley Department of Genetics Collection contains a selective sampling of correspondence relating to the organization and early history of the nation's first Department of Genetics. Centered in the years 1912-1930, the collection consists primarily of correspondence to and from Babcock and Clausen, pertaining to their research, administrative matters, and the genetical community. Prominent among their correspondents are George H. Shull, Thomas Hunt Morgan, A. H. Sturtevant, and H. J. Muller.

The geneticist Milislav Demerec emigrated from Yugloslavia in 1919, spending nearly his entire career in the Department of Genetics at Cold Spring Harbor Laboratory. Working initially on the genetics of maize and later on Drosophila virilis, his research interests included radiation and chemical mutagenesis, and during the Second World War, penicillin and the genetics of antibiotic resistance. Demerec served as head of the laboratory at Cold Spring Harbor from 1941 until 1960. The Demerec collection contains the extant professional papers of Milislav Demerec, dating primarily from the time of his arrival at Cold Spring Harbor until his retirement. In addition to his correspondence with colleagues, the collection includes interesting material on the administration of Cold Spring Harbor laboratory during the 1940s and 1950s, data and research notes, material relating to professional organizations (e.g. Genetics Society of America, American Society of Naturalists), a lengthy series of lectures given by Demerec, and a large number of photographs pertaining to Demerec's research, but also to his colleagues and Cold Spring Harbor itself. There is also a Register of visitors to the laboratory (1927-1945) and a Milislav Demerec reprint list.