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History of Genetics Seminar: Continuous Variation

History of Genetics Seminar: Continuous Variation

Presentation I gave in a class I'm taking/took

Gitanshu Munjal

October 29, 2015
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  1. Turn of the century - Bateson [Mendelism] vs Weldon [Law

    of Ancestral Inheritance] - Galton meets his “statistical heir” (Pearson) via Weldon Public domain picture of Sir Francis Galton Image Credit: Wikimedia Commons
  2. Karl Pearson - Extremely well educated in multiple disciplines (Mathematics,

    Physics, Physiology, Darwinism, Roman Law, German Literature) “Have you ever attempted to conceive all there is in the world worth knowing— that not one subject in the universe is unworthy of study? The giants of literature, the mysteries of many-dimensional space, the attempts of Boltzmann and Crookes to penetrate Nature's very laboratory, the Kantian theory of the universe, and the latest discoveries in embryology, with their wonderful tales of the development of life—what an immensity beyond our grasp! [...] Mankind seems on the verge of a new and glorious discovery. What Newton did to simplify the planetary motions must now be done to unite in one whole the various isolated theories of mathematical physics.” ~ The New Werther Public domain picture of Karl Pearson Image Credit: Wikimedia Commons
  3. Karl Pearson - Extremely well educated in multiple disciplines -

    The Grammar of Science - Assisted by female mathematicians - Galton’s Protégé - Proponent of eugenics - First holder of the Galton Chair of Eugenics (now Genetics) - Founded annals of Eugenics (now Human Genetics) - Correlation coefficient, chi-squared, hypothesis testing, PCAs …coefficient of racial likeness (computed from skull measurements) Public domain picture of Karl Pearson Image Credit: Wikimedia Commons
  4. Turn of the century - Bateson [Mendelism] vs Weldon [Law

    of Ancestral Inheritance] - Galton meets his “statistical heir” (Pearson) via Weldon - Bateson [Mendelism] vs Weldon/Pearson [Biometric thinking] - Yule suggests Ancestral Inheritance as a case of Mendelian principles in a random-breeding population * (1902) - Pearson retaliates with contradicting observational data (1904) - Yule criticizes assumptions (complete dominance of all gene pairs) (1906) - General agreement that many genes would influence traits like height (i.e. traits that are putatively affected by lots of “elements”) - Enter Johanssen… Public domain picture of Sir Francis Galton Image Credit: Wikimedia Commons
  5. Wilhelm Johannsen - Botanist, plant physiologist, geneticist - Trained as

    a pharmacist - Pure lines: genotype, phenotype, gene (!= pangene) Wilhelm Johannsen Image Credit: Wikimedia Commons
  6. Wilhelm Johannsen - Botanist, plant physiologist, geneticist - Trained as

    a pharmacist - Pure lines: genotype, phenotype, gene (!= pangene) Wilhelm Johannsen Image Credit: Wikimedia Commons Figure for illustration purposes only
  7. Wilhelm Johannsen - Botanist, plant physiologist, geneticist - Trained as

    a pharmacist - Pure lines: genotype, phenotype, gene (!= pangene) Wilhelm Johannsen Image Credit: Wikimedia Commons Figure for illustration purposes only
  8. Wilhelm Johannsen - Botanist, plant physiologist, geneticist - Trained as

    a pharmacist - Pure lines: genotype, phenotype, gene (!= pangene) Post-selfing Wilhelm Johannsen Image Credit: Wikimedia Commons Figure for illustration purposes only
  9. Wilhelm Johannsen - Botanist, plant physiologist, geneticist - Trained as

    a pharmacist - Pure lines: genotype, phenotype, gene (!= pangene) - Pure lines and opposition to normally distributed trait variation as raw materials for selection - Biometrical school offers no insights into the mechanisms underlying phenotypes BUT provides useful statistical methods Wilhelm Johannsen Image Credit: Wikimedia Commons
  10. Edward Murray East Early Professional Career: Edward Murray East Creative

    Commons Picture: http://hdl.handle.net/10776/3253 UIUC long-term selection experiment for oil and protein in corn Data from http://hdl.handle.net/2142/3526
  11. Edward Murray East Early Professional Career: - Spends 5 years

    at the Illinois station - Notices increase/decrease in protein/oil content associates with decrease in yield; becomes interested in inbreeding and cross-breeding. - Moves to New Haven to work with Jenkins (1905, receives Master in 1904) - Early formative work on tobacco, potato, maize - Learns of Shull’s work; discards idea of crossing inbred strains for crop improvement as of “less practical value” - Moves to Harvard in capacity of an Assistant Professor (1909); - Promoted to full professor (1914) Edward Murray East Creative Commons Picture: http://hdl.handle.net/10776/3253
  12. Edward Murray East - Jones’ memoir - Communications between East

    and Shull “Since studying your paper, I agree entirely with your conclusion [The composition of a field of maize] and wonder why I have been so stupid as not to see the fact myself ..” ~ East to Shull (1908) Edward Murray East Creative Commons Picture: http://hdl.handle.net/10776/3253
  13. Edward Murray East - Jones’ memoir - Communications between East

    and Shull “I am convinced that there is a wide open field here which has not been touched heretofore. There is little doubt in my mind that if I had held on to my idea of the composition of a field of corn…I could have raised a monument to myself which would be worthy to stand with the best biological work of recent times. But the matter seemed to me of too great importance in view of the value of our maize crop to selfishly keep it to myself longer than was necessary to assure myself of its correctness” ~ Shull to East (1908) Edward Murray East Creative Commons Picture: http://hdl.handle.net/10776/3253
  14. Edward Murray East - Jones’ memoir - Communications between East

    and Shull “I did not know that you were continuing this work…I thought that my idea…was a new idea…I feel that the method I have outlined will be much more practical than the one you have outlined” ~ East to Shull (1909) Edward Murray East Creative Commons Picture: http://hdl.handle.net/10776/3253
  15. Edward Murray East - Jones’ memoir - Communications between East

    and Shull “…I care very little for the question of priority. What we are most concerned in is the triumph of truth and especially of useful truth…” ~ Shull to East (1909) Edward Murray East Creative Commons Picture: http://hdl.handle.net/10776/3253
  16. X Tom Stilwell Google Images CC Image by Jonathunder https://commons.wikimedia.org/

    wiki/File:YellowCorn.jpg “Popped Secret: The Mysterious Origin of Corn” HHMI
  17. 159 Dark Yellow 145 Light Yellow 1:1 ratio in F1

    Infer pollen parent was Y1 Y1 Y2 y2 “Popped Secret: The Mysterious Origin of Corn” HHMI
  18. 159 Dark Yellow 145 Light Yellow self self “Popped Secret:

    The Mysterious Origin of Corn” HHMI
  19. Rep 2: Reverse gender and color Essentially same results Rep

    3: No 15:1 obtained Experiment confounded by additional traits “Popped Secret: The Mysterious Origin of Corn” HHMI
  20. East’s Insight: - Reconciling Mendelian Principles with Quantitative variation -

    “In certain cases it would appear that we may have several alleloniorphicpairs each of which is inherited independently of the others, and each of which is separately capable of forming the same character. When present in different numbers, in different individuals, these units simply form quantitative differences.” - “It may be that there is a kind of biological isomerism, in which, instead of molecules of the same formula having different physical properties, there are isomers capable of forming the same character, although, through difference in construction, they are not allelomorphic to each other.” - Suggests isolation of these isomers due to descent leading to the appearance as polymorphic and also the possibility of linkage (though not explicitly) leading to the appearance as monomorphic. “Popped Secret: The Mysterious Origin of Corn” HHMI
  21. East’s Insight: - Consider ABCD x abcd - What is

    the probability of recovering aabbccdd in F2? - When a smaller population is considered, it will appear to be a blend of the two parents with a fluctuating variability on each side of its mode. - Complete dominance is rare and so the distribution approaches a normal curve due to small variations at multiple sites and environmental differences - Consider ABcd X abCD “Popped Secret: The Mysterious Origin of Corn” HHMI
  22. - Kernel Row Number “Popped Secret: The Mysterious Origin of

    Corn” HHMI Figure reproduced from Liu et al, 2015
  23. X Hybrid Vigor “Popped Secret: The Mysterious Origin of Corn”

    HHMI “Popped Secret: The Mysterious Origin of Corn” HHMI
  24. “Popped Secret: The Mysterious Origin of Corn” HHMI “Popped Secret:

    The Mysterious Origin of Corn” HHMI “Popped Secret: The Mysterious Origin of Corn” HHMI
  25. Hybrid Vigor Complementation? - East rejects at first - Jones

    points out new possibilities in light of linkage “Popped Secret: The Mysterious Origin of Corn” HHMI
  26. Hybrid Vigor Does how/why matter in context of application? “Popped

    Secret: The Mysterious Origin of Corn” HHMI
  27. References • Coe, Edward H. "The origins of maize genetics."

    Nature Reviews Genetics 2.11 (2001): 898-905 • Crow, James F. "90 years ago: the beginning of hybrid maize." Genetics 148.3 (1998): 923-928. • East, Edward M. "A Mendelian interpretation of variation that is apparently continuous." American Naturalist (1910): 65-82. • East, E. M. "Studies on size inheritance in Nicotiana." Genetics 1.2 (1916): 164. • Jones Donald, F. "Biographical Memoir of Edward Murray East (1879-1938)." National Academy of Sciences, Autumn meeting. 1944. • Liu, Lei, et al. "Genetic architecture of maize kernel row number and whole genome prediction." Theoretical and Applied Genetics (2015): 1-12. • Nelson, Oliver E. "A notable triumvirate of maize geneticists." Genetics 135.4 (1993): 937. • Poole, C. F. "Improvement of sweet corn." US Dept. Agric. Yearbook (1937). • Sturtevant, A. H. "A History of Genetics." Harper & Row, New York (1965).