Wilhelm Johannsen

Infobox_Scientist
name = Wilhelm Ludvig Johannsen


birth_date = birth date|1857|02|03
birth_place = Elsinore, Denmark
nationality = DEN
death_date = death date and age|1927|11|11|1857|02|03
death_place = Copenhagen, Denmark
field = Genetics
Plant physiology
work_institution = University of Copenhagen
alma_mater = University of Copenhagen
doctoral_advisor =
doctoral_students =
known_for = proving the constancy of the genome
defining gene, genotype and phenotype
prizes =
footnotes =

Wilhelm Johannsen (February 3, 1857 - November 11, 1927) was a Danish botanist, plant physiologist and geneticist. He was born in Copenhagen. Very young, he was apprenticed to a pharmacist in 1872 and worked in Denmark and Germany, 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 [Warming, Eug. & W. Johannsen (1895) Den almindelige Botanik (General Botany): En Lærebog, nærmest til Brug for Studerende og Lærere. 3rd edn, Kjøbenhavn. 4th edn by Warming and Johannsen 1900-01). German edn 1907-09: Lehrbuch der allgemeinen Botanik (from the 4th edn, by E. P. Meinecke). Berlin, Borntraeger. 667 pp.] . His most well-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". His 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 [ [http://dx.doi.org/10.1111/j.1600-0498.1979.tb00589.x Roll-Hansen, Nils (1979) The Genotype Theory of Wilhelm Johannsen and its Relation to Plant Breeding and the Study of Evolution. Centaurus 22 (3): 201–235] ] . Only with the modern evolutionary synthesis, it was established that variation need tobe heritable to act as the raw material for selection.The terms "phenotype" and "genotype" were created by Wilhelm Johannsen and first used in his paper "Om arvelighed i samfund og i rene linier" [Johannsen, W. (1903) Om arvelighed i samfund og i rene linier. Oversigt over det Kongelige Danske Videnskabernes Selskabs Forhandlinger, vol. 3: 247-270.] and in his book "Arvelighedslærens Elementer" [Johannsen, W.L. (1905) Arvelighedslærens elementer (The Elements of Heredity). Copenhagen.] . This book was rewritten, enlarged and translated to German as "Elemente der exakten Erblichkeitslehre" [Johannsen, W. (1909) Elemente der exakten Erblichkeitslehre. Gustav Fischer, Jena.] . It was in this book Johannsen 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 vicechancelor 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 [ [http://links.jstor.org/sici?sici=0003-0147%28191103%2945%3A531%3C129%3ATGCOH%3E2.0.CO%3B2-M Johannsen, W. (1911) The Genotype Conception of Heredity. American Naturalist 45 (531): 129-159.] ] . In 1911, he was invited to give a series of four lectures at Columbia University [ [http://links.jstor.org/sici?sici=0036-8075%2819111013%293%3A34%3A876%3C484%3APJCL%3E2.0.CO%3B2-3 Anon. (1911) Professor Johannsen's Columbia Lectures. Science N.S. 34 (876): 484.] ]

Miscellaneous

Corresponding member of the Academy of Natural Sciences of Philadelphia (elected 1915).

References

*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.
* [http://links.jstor.org/sici?sici=0306-3127%28198311%2913%3A4%3C481%3ATDOSGA%3E2.0.CO%3B2-2 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.]
* [http://links.jstor.org/sici?sici=0306-3127%28199111%2921%3A4%3C649%3AOTROJP%3E2.0.CO%3B2-0 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

* [http://www.wjc.ku.dk/ Wilhelm Johannsen Centre for Functional Genome Research]
* [http://www.wjc.ku.dk/wilhelm/index.php?subpage=gallery Image gallery]
* [http://www.wjc.ku.dk/library/video/original.avi 6 min silent mowie showing Johannsen in action as teacher and scientist]