09-13 mendel heredity

09-13 mendel heredity - Gregor Mendel Historical Context...

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Gregor Mendel – Historical Context Gregor Mendel, Austrian monk living in Brunn (now Brno, Czech Republic) Educated at the University of Vienna Two existing paradigms in 1864: Blending hypothesis – phenotypes are the result of blending of characteristics present in the two parents Acquired characteristics hypothesis – phenotypes in offspring are the result of exposure of the parents to environmental stresses or use of that trait by the parents Also known as Lamarckian inheritance http://www.mcah.columbia.edu/dbcourses/ris eofciv/medium/LAMARCK.jpg Jean-Baptiste Lamarck
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Mendel’s Co-Discoverers - #1 Erich Tschermak von Seysenegg (1871-1962) The simultaneous discovery of Mendel by Correns, by de Vries, and myself appears to me especially gratifying… 7 pg summary of his Ph.D. thesis: Regularly, one character in question…comes exclusively into expression (dominating character according to Mendel) in contrast to the recessive character…. . The appearance of the dominating and the recessive character is not a purely exclusive one. In individual cases, I could, on the contrary, detect with certainty a simultaneous appearance of both, that is to say, of transition stages .”
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Mendel’s Co-Discoverers - #2 Hugo Marie de Vries (1845-1935) Eminent botanist of the late 1800’s Described 2:1 segregation data, which he reported as 3:1 data after reading Mendel’s work 1897: Lychnis segregation of 99 hairy:54 glabrous reported as conforming to a 3:1 ratio when published in 1900…!
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Mendel’s Co-Discoverers - #3 Carl Erich Correns (1864-1933) Identified the 9:3:3:1 ratio Most accurately the “rediscoverer” of Mendel
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William Bateson (1861-1926) Opponent of Darwin’s idea of intermediate phenotypes Consequently, he was attracted to Mendel’s dominance/recessivity model Coined the term genetics
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Mendel and His Peas Hybridization of the common pea Closed flowers = pea plants are naturally inbred ( true breeding )
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Mendel’s Seven Traits Mendel made monohybrids – he crossed pea varieties expressing one trait each in pairwise combinations Freeman Fig. 10.2
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Pure Line Crosses Freeman Fig. 10.4 Pure lines crossed will produce uniform progeny
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09-13 mendel heredity - Gregor Mendel Historical Context...

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