Wilhelm Ludwig Johannsen

Born Feb. 3, 1857, in Copenhagen; died there Nov. 11, 1927. Danish biologist; one of the founders of contemporary genetics. Professor at the Institute of Plant Physiology of the University of Copenhagen; member of the Swedish Academy of Sciences.

With his experiments (1898–1903) in the selection of quantitative characters in barley and beans, Johannsen proved that selection is not effective in the offspring of self-pollinating plants. With this he refuted the theories of F. Galton (1889, 1897) on the partial inheritance of individual deviations of organisms. The doctrine created by Johannsen on this foundation of pure lines has become the basis for modern principles of selection and has shown the nonheritability of characters acquired by organisms during their lifetimes and the role of heredity in the processes of natural selection. In his work Elements of the Precise Study of Heredity (1909), Johannsen gave an analysis of the basic concepts of genetics and introduced the terms “gene,” “genotype,” and “phenotype.” However, Johannsen took the position of an agnostic on the problems of the material nature of the gene and the role of genetics in elaborating problems of evolution.