Wilhelm Johannsen

Wilhelm Johannsen (3 February 1857 – 11 November 1927) was a Danish pharmacist, botanist, plant physiologist, and geneticist. He is best known for coining the terms gene, phenotype and genotype, and for his 1903 "pure line" experiments in genetics.

Biography

Johannsen was born in Copenhagen. While very young, he was apprenticed to a pharmacist and worked in Denmark and Germany beginning in 1872 until passing his pharmacist's exam in 1879. In 1881, he became assistant in the chemistry department at the Carlsberg Laboratory under the chemist Johan Kjeldahl. Johannsen studied the metabolism of dormancy and germination in seeds, tubers and buds. He showed that dormancy could be broken by various anesthetic compounds, such as diethyl ether and chloroform.

In 1892, he was appointed lecturer at Royal Veterinary and Agricultural University and later became professor of botany and plant physiology. He taught plant physiology. His best-known research concerned so-called ''pure lines'' of the self-fertile common bean. He was able to show that even in populations homozygous for all traits, i.e. without genetic variation, seed size followed a normal distribution. This was attributable to resource provision to the mother plant and to the position of seeds in pods and of pods on the plant. This led him to coin the terms ''phenotype'' and '' genotype''.

Johannsen's findings led him to oppose contemporary Darwinists, most notably Francis Galton and Karl Pearson, who held the occurrence of normal distributed trait variation in populations as proof of gradual genetic variation on which selection could act. Only with the modern synthesis, was it established that variation needed to be heritable to act as the raw material for selection.

He created the terms ''phenotype'' and '' genotype'', first using them in his book in German as ''Elemente der exakten Erblichkeitslehre'' (Elements of the exact theory of heredity). This book was based in large part on ''Om arvelighed i samfund og i rene linier'' ("On heredity in society and in pure lines") and in his book ''Arvelighedslærens Elementer''. It was in this book Johannsen also introduced the term ''gene''. This term was coined in opposition to the then common ''pangene'' that stemmed from Darwin's theory of pangenesis. The book became one of the founding texts of genetics.

Also in 1905, Johannsen was appointed professor of plant physiology at the University of Copenhagen, becoming vice-chancellor in 1917. In December 1910, Johannsen was invited to give an address before the American Society of Naturalists. This talk was printed in the American Naturalist. In 1911, he was invited to give a series of four lectures at Columbia University.

Johannsen was a corresponding member of the Academy of Natural Sciences of Philadelphia (elected 1915).

References

Sources

*Anker, Jean (1932) Wilhelm Johannsen, pp. 177–180 in: Meisen, V. Prominent Danish Scientists through the Ages. University Library of Copenhagen 450th Anniversary. Levin & Munksgaard, Copenhagen.
* Roll-Hansen, Nils (1983) The Death of Spontaneous Generation and the Birth of the Gene: Two Case Studies of Relativism. Social Studies of Science 13 (4): 481–519.
*Kim, Kyung-Man (1991) On the Reception of Johannsen's Pure Line Theory: Toward a Sociology of Scientific Validity. Social Studies of Science 21 (4): 649–679.

External links

Wilhelm Johannsen Centre for Functional Genome ResearchImage gallery6 min silent movie showing Johannsen in action as teacher and scientist

{{DEFAULTSORT:Johannsen, Wilhelm
1857 births
1927 deaths
20th-century Danish botanists

Agriculture educators
Danish science writers
University of Copenhagen alumni
University of Copenhagen faculty
People from Helsingør
Carlsberg Laboratory staff
Plant physiologists
Danish geneticists
Rectors of the University of Copenhagen
19th-century Danish botanists
Members of the Royal Society of Sciences in Uppsala