Johannsen, Wilhelm Ludvig


Johannsen, Wilhelm Ludvig
born Feb. 3, 1857, Copenhagen, Den.
died Nov. 11, 1927, Copenhagen

Danish botanist and geneticist.

He supported Hugo de Vries's discovery that variation in genotype can occur by mutation; the new character, while independent of natural selection in its initial occurrence, is then subject to natural selection. Johannsen's Elements of Heredity (1909) became an influential text, and his terms phenotype and genotype are now a part of the language of genetics.

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▪ Danish botanist and geneticist
born Feb. 3, 1857, Copenhagen, Den.
died Nov. 11, 1927, Copenhagen

      Danish botanist and geneticist whose experiments in plant (plant breeding) heredity offered strong support to the mutation theory of the Dutch botanist Hugo de Vries (that changes in heredity come about through sudden, discrete changes of the heredity units in germ cells). Many geneticists thought Johannsen's ideas dealt a severe blow to Charles Darwin's theory that new species were produced by the slow process of natural selection.

      Johannsen studied in Copenhagen, Germany, and Finland and was a professor first at the Institute of Agriculture in Denmark and then at the University of Copenhagen. After working initially in plant physiology, he devoted himself entirely to experimental research in heredity, becoming a leading authority in that subject. He found in studies with princess beans that in the succession of individuals arising from a single seed there existed what he termed a “pure line,” in which the hereditary units of all individuals are the same. About 1905 he demonstrated that he could produce large or small plants from beans of corresponding size. He concluded that although the plants differed in external characteristics, or in their “phenotype,” they nevertheless carried identical hereditary units or, in other words, preserved a common “genotype”; his terms phenotype and genotype are now a part of the language of genetics. Johannsen supported de Vries' discovery that variation in genotype can occur by mutation; that is, as a sudden, spontaneous appearance of a new species character. The new character, while independent of natural selection in its initial occurrence, is then subject to natural selection, as described by Darwin, as it either survives or disappears in future generations.

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Universalium. 2010.

Look at other dictionaries:

  • Johannsen, Wilhelm Ludvig — (3 feb. 1857, Copenhague, Dinamarca–11 nov. 1927, Copenhague). Botánico y genetista danés. Respaldó el descubrimiento de Hugo de Vries, de que la variación del genotipo puede ocurrir por mutación; el nuevo carácter, si bien independiente de la… …   Enciclopedia Universal

  • Wilhelm Ludvig Johannsen — Wilhelm Johannsen Portrait de Johannsen Wilhelm Ludvig Johannsen est un botaniste danois, né 3 février 1857 à Copenhague et mort le 11 novembre 1927 dans cette même ville. Il travaille pour l Institut agricole de Copenhague avant d enseigner l… …   Wikipédia en Français

  • Wilhelm Ludvig Johannsen — Porträtfoto von Johannsen Wilhelm Ludvig Johannsen (* 3. Februar 1857 in Kopenhagen; † 11. November 1927) war ein dänischer Botaniker und Genetiker. Er prägte den Begriff „Gen“ als Träger der Vererbung …   Deutsch Wikipedia

  • Wilhelm Johannsen — Porträtfoto von Johannsen Wilhelm Ludvig Johannsen (* 3. Februar 1857 in Kopenhagen; † 11. November 1927) war ein dänischer Botaniker und Genetiker. Er prägte den Begriff „Gen“ als Träger der Vererbung …   Deutsch Wikipedia

  • Wilhelm Johannsen — Portrait de Johannsen Wilhelm Ludvig Johannsen est un botaniste danois, né 3 février 1857 à Copenhague et mort le 11 novembre 1927 dans cette même ville. Il travaille pour l Institut agricole de Copenhague avant d enseigner l agriculture à l… …   Wikipédia en Français

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