Johanssen, Wilhelm Ludvig (1857–1927)

Danish botanist and founder of modern genetics who coined the term gene as the unit of heredity (although it was not known at the time to consist of DNA in cells). He introduced the concept of an organism having a ‘genotype’ (set of variable genes) and ‘phenotype’ (characteristics produced by the presence of certain genes). He also studied the metabolism of germination (the initial stages of growth in a seed) in plants.

Johanssen was born in Copenhagen, Denmark. As he came from a poor family he could not afford to attend university and was apprenticed to a pharmacist 1872. He taught himself chemistry in his spare time, before working in Germany, where he developed an interest in botany. In 1879, he returned to Denmark, and, after passing his pharmacology exams, became an assistant in the Carlsberg laboratory where he worked on the metabolism of germination in plants. He was made a lecturer at Copenhagen Agricultural College 1892 and professor of botany and plant physiology 1903.