Wilhelm Johannsen Describes Genetic Variability, Phenotype and Genotype

In 1903 the Danish geneticist Wilhelm Johannsen issued Ueber Erblichkeit in Populationen und in reinem Linien. This work, published in Jena by Georg Fischer, provided more support for the Mendelian laws of inheritance by showing that in certain self-fertilizing plants a pure line of descendants can be maintained indefinitely, in which case natural selection is not effective; selection depends upon genetic variability.

In "Om arvelighed i samfund og i rene linier," Oversigt over det Kongelige Danske Videnskabernes Selskabs Forhandlinger, 3 (1903) 247-270, Johannsen coined the terms phenotype and genotype. Johannsen pubished a German translation of this paper in Ueber Erblichkeit....