Gregor Mendel

Gregor Mendel
Born Johann Mendel
(1822-07-20)20 July 1822
Heinzendorf bei Odrau, Silesia, Austrian Empire (now Hynčice, Czech Republic)
Died 6 January 1884(1884-01-06) (aged 61)
Brno, Austria-Hungary (now Czech Republic)
Nationality Austrian
Fields Genetics
Institutions St Thomas's Abbey
Alma mater University of Olomouc
University of Vienna
Known for Creating the science of genetics

Gregor Johann Mendel (Czech: Řehoř Jan Mendel;[1] 20 July 1822[2] – 6 January 1884) was a German-speaking Moravian-Silesian[3] scientist and Augustinian friar and abbot of St. Thomas' Abbey in Brno who gained posthumous fame as the founder of the modern science of genetics. Though farmers had known for centuries that crossbreeding of animals and plants could favor certain desirable traits, Mendel's pea plant experiments conducted between 1856 and 1863 established many of the rules of heredity, now referred to as the laws of Mendelian inheritance.[4]

Mendel worked with seven characteristics of pea plants: plant height, pod shape and color, seed shape and color, and flower position and color. With seed color, he showed that when a yellow pea and a green pea were bred together their offspring plant was always yellow. However, in the next generation of plants, the green peas reappeared at a ratio of 1:3. To explain this phenomenon, Mendel coined the terms “recessive” and “dominant” in reference to certain traits. (In the preceding example, green peas are recessive and yellow peas are dominant.) He published his work in 1866, demonstrating the actions of invisible “factors”—now called genes—in providing for visible traits in predictable ways.

The profound significance of Mendel's work was not recognized until the turn of the 20th century (more than three decades later) with the independent rediscovery of these laws.[5] Erich von Tschermak, Hugo de Vries, Carl Correns, and William Jasper Spillman independently verified several of Mendel's experimental findings, ushering in the modern age of genetics.[6]

Life and career

Mendel was born into an German-speaking family in Heinzendorf bei Odrau, Moravian-Silesian border, Austrian Empire (now Hynčice, Czech Republic). He was the son of Anton and Rosine (Schwirtlich) Mendel, and had one older sister, Veronika, and one younger, Theresia. They lived and worked on a farm which had been owned by the Mendel family for at least 130 years.[7] During his childhood, Mendel worked as a gardener and studied beekeeping. Later, as a young man, he attended gymnasium in Opava (called Troppau in German). He had to take four months off during his gymnasium studies due to illness. From 1840 to 1843, he studied practical and theoretical philosophy and physics at the Philosophical Institute of the University of Olomouc, taking another year off because of illness. He also struggled financially to pay for his studies, and Theresia gave him her dowry. Later he helped support her three sons, two of whom became doctors.

He became a friar because it enabled him to obtain an education without having to pay for it himself.[8] He was given the name Gregor (Řehoř in Czech)[1] when he joined the Augustinian friars.[9])

When Mendel entered the Faculty of Philosophy, the Department of Natural History and Agriculture was headed by Johann Karl Nestler who conducted extensive research of hereditary traits of plants and animals, especially sheep. Upon recommendation of his physics teacher Friedrich Franz,[10] Mendel entered the Augustinian St Thomas's Abbey in Brno (called Brünn in German) and began his training as a priest. Born Johann Mendel, he took the name Gregor upon entering religious life. Mendel worked as a substitute high school teacher. In 1850 he failed the oral part, the last of three parts, of his exams to become a certified high school teacher. In 1851 he was sent to the University of Vienna to study under the sponsorship of Abbot C. F. Napp so that he could get more formal education.[11] At Vienna, his professor of physics was Christian Doppler.[12] Mendel returned to his abbey in 1853 as a teacher, principally of physics. In 1856 he took the exam to become a certified teacher and again failed the oral part.[11] In 1867 he replaced Napp as abbot of the monastery.[13]

After he was elevated as abbot in 1868, his scientific work largely ended, as Mendel became consumed with his increased administrative responsibilities, especially a dispute with the civil government over their attempt to impose special taxes on religious institutions.[14] Mendel died on 6 January 1884, at the age of 61, in Brno, Moravia, Austria-Hungary (now Czech Republic), from chronic nephritis. Czech composer Leoš Janáček played the organ at his funeral. After his death, the succeeding abbot burned all papers in Mendel's collection, to mark an end to the disputes over taxation.[15]

Experiments on plant hybridization

Dominant and recessive phenotypes. (1) Parental generation. (2) F1 generation. (3) F2 generation.

Gregor Mendel, who is known as the "father of modern genetics", was inspired by both his professors at the Palacký University, Olomouc, (Friedrich Franz and Johann Karl Nestler) and his colleagues at the monastery (such as Franz Diebl) to study variation in plants. In 1854 Napp authorized Mendel for the investigation, who conducted his study in the monastery's 2 hectares (4.9 acres) experimental garden,[16] which was originally planted by Napp in 1830.[13] Unlike Nestler, who studied hereditary traits in sheep, Mendel focused on plants. After initial experiments with pea plants, Mendel settled on studying seven traits that seemed to inherit independently of other traits: seed shape, flower color, seed coat tint, pod shape, unripe pod color, flower location, and plant height. He first focused on seed shape, which was either angular or round.[17] Between 1856 and 1863 Mendel cultivated and tested some 28,000 plants, majority of which were pea plants (Pisum sativum).[18][19][20] This study showed that one in four pea plants had purebred recessive alleles, two out of four were hybrid and one out of four were purebred dominant. His experiments led him to make two generalizations, the Law of Segregation and the Law of Independent Assortment, which later came to be known as Mendel's Laws of Inheritance.[21]

Mendel presented his paper, "Versuche über Pflanzenhybriden" ("Experiments on Plant Hybridization"), at two meetings of the Natural History Society of Brno in Moravia on 8 February and 8 March 1865.[22] It was received favorably and generated reports in several local newspapers.[23] When Mendel's paper was published in 1866 in Verhandlungen des naturforschenden Vereins Brünn,[24] it was seen as essentially about hybridization rather than inheritance and had little impact and was cited about three times over the next thirty-five years. His paper was criticized at the time, but is now considered a seminal work.[25] Notably, Charles Darwin was unaware of Mendel's paper, and it is envisaged that if he had, genetics would have been a much older science.[26][27]

Other experiments

Mendel began his studies on heredity using mice. He was at St. Thomas's Abbey but his bishop did not like one of his friars studying animal sex, so Mendel switched to plants.[28] Mendel also bred bees in a bee house that was built for him, using bee hives that he designed.[29] He also studied astronomy and meteorology,[13] founding the 'Austrian Meteorological Society' in 1865.[12] The majority of his published works were related to meteorology.[12]

Mendel also experimented with hawkweed[30] and honeybees. However, none of his results on these survived, except for passing mention in the reports of Moravian Apiculture Society.[31] All that is known definitely is that he used Cyprian and Carniolan bees,[32] which were particularly aggressive to the annoyance of other monks and visitors of the monastery such that he was asked to get rid of them.[33] In contrast, he had a fondness for the bees, and refer to them as "my dearest little animals".[34]

He also described novel plant species, and these are denoted with the botanical author abbreviation "Mendel".

Rediscovery of Mendel's work

Mendel's work was rejected at first in the scientific community, and was not widely accepted until after he died. During his own lifetime, most biologists held the idea that all characteristics were passed to the next generation through blending inheritance, in which the traits from each parent are averaged together. Instances of this phenomenon are now explained by the action of multiple genes with quantitative effects. Charles Darwin tried unsuccessfully to explain inheritance through a theory of pangenesis. It was not until the early twentieth century that the importance of Mendel's ideas was realized.

By 1900, research aimed at finding a successful theory of discontinuous inheritance rather than blending inheritance led to independent duplication of his work by Hugo de Vries and Carl Correns, and the rediscovery of Mendel's writings and laws. Both acknowledged Mendel's priority, and it is thought probable that de Vries did not understand the results he had found until after reading Mendel.[5] Though Erich von Tschermak was originally also credited with rediscovery, this is no longer accepted because he did not understand Mendel's laws.[35] Though de Vries later lost interest in Mendelism, other biologists started to establish genetics as a science.[5] All three of these researchers, each from a different country, published their work rediscovering Mendel's work within a two-month span in the Spring of 1900.[36]

Mendel's results were quickly replicated, and genetic linkage quickly worked out. Biologists flocked to the theory; even though it was not yet applicable to many phenomena, it sought to give a genotypic understanding of heredity which they felt was lacking in previous studies of heredity which focused on phenotypic approaches. Most prominent of these previous approaches was the biometric school of Karl Pearson and W. F. R. Weldon, which was based heavily on statistical studies of phenotype variation. The strongest opposition to this school came from William Bateson, who perhaps did the most in the early days of publicising the benefits of Mendel's theory (the word "genetics", and much of the discipline's other terminology, originated with Bateson). This debate between the biometricians and the Mendelians was extremely vigorous in the first two decades of the twentieth century, with the biometricians claiming statistical and mathematical rigor,[37] whereas the Mendelians claimed a better understanding of biology.[38][39] (Modern genetics shows that Mendelian heredity is in fact an inherently biological process, though not all genes of Mendel's experiments are yet understood.)[40][41]

In the end, the two approaches were combined, especially by work conducted by R. A. Fisher as early as 1918. The combination, in the 1930s and 1940s, of Mendelian genetics with Darwin's theory of natural selection resulted in the modern synthesis of evolutionary biology.[42][43]

Controversy

Mendel's experimental results have later been the object of considerable dispute.[15] Mendel used crosses between true-breeding (homozygous) pea plants for each of the seven traits. In each case the offspring (F1) would be heterozygous and would therefore display the dominant state uniformly (such as round or green peas). In 1936, R.A. Fisher reconstructed Mendel's experiments, analyzed results from the F2 (second filial) generation and found the ratio of dominant to recessive phenotypes (e.g. green versus yellow peas; round versus wrinkled peas) to be implausibly close to the expected ratio of 3 to 1.[44][45] Mendel allowed pea plants showing the dominant phenotype to self-fertilize in order to determine the ratio of homozygotes to heterozygotes from the occurrence of recessive phenotype progeny. Fisher was sceptical of Mendel's 1:2 ratio of true-breeding (homozygotes) to mixed progeny (heterozygotes), and remarked Mendel's results as, "Too good to be true."[46] In particular, Fisher suggested that Mendel inferred parental phenotype by examination of 10 progeny, but did not adjust his expectation for the probability that a heterozygote parent could produce 10 dominant phenotype offspring (this occurs with a frequency of 0.7510 = 6% of tests). Thus corrected one should expect a ratio of 1.7:1, quite different from Mendel's results of 720:353, which are an extremely close fit to Mendel's incorrect expectation of 2:1.[44] This statistical interpretation was taken as the ground for criticising Mendel's works as a whole, in 1998 amounting to an accusation of experimental fraud by removing outliers, "tidying" datasets and repeating experiments.[47] Fisher asserted, that "the data of most, if not all, of the experiments have been falsified so as to agree closely with Mendel's expectations,"[44] and he called Mendel's result "abominable", "shocking",[48] and "cooked".[49]

Fisher accused Mendel's experiments as "biased strongly in the direction of agreement with expectation... to give the theory the benefit of doubt".[44] This has been often cited as an example of confirmation bias.[50] This might arise if he detected an approximate 3 to 1 ratio early in his experiments with a small sample size, and, in cases where the ratio appeared to deviate slightly from this, continued collecting more data until the results conformed more nearly to an exact ratio. In his 2004, J.W. Porteous concluded that Mendel's observations were implausible.[51] However, reproduction of the experiments has demonstrated that there is no real bias towards Mendel's data.[52] In 2007, Daniel L. Hartl and Daniel J. Fairbanks suggested that Fisher incorrectly interpreted these experiments. They found it likely that Mendel scored more than 10 progeny, and that the results matched the expectation. They conclude, "Fisher's allegation of deliberate falsification can finally be put to rest, because on closer analysis it has proved to be unsupported by convincing evidence."[48][53] In 2008 Hartl and Fairbanks (with Allan Franklin and AWF Edwards) wrote a comprehensive book in which they concluded that there were no reasons to assert Mendel fabricated his results, nor that Fisher deliberately tried to diminish Mendel's legacy.[54] Reassessment of the statistical analyses also disprove the notion of confirmation bias in Mendel's results.[55][56]

See also

References

  1. 1 2 Funeral card in Czech (Brno, 6. January 1884)
  2. ↑ 20 July is his birthday; often mentioned is 22 July, the date of his baptism. Biography of Mendel at the Mendel Museum
  3. ↑ Moravané a Češi
  4. ↑ https://history.nih.gov/exhibits/nirenberg/HS1_mendel.htm
  5. 1 2 3 Bowler, Peter J. (2003). Evolution: the history of an idea. Berkeley: University of California Press. ISBN 0-520-23693-9.
  6. ↑ https://history.nih.gov/exhibits/nirenberg/HS1_mendel.htm
  7. ↑ Gregor Mendel, Alain F. Corcos, Floyd V. Monaghan, Maria C. Weber "Gregor Mendel's Experiments on Plant Hybrids: A Guided Study", Rutgers University Press, 1993.
  8. ↑ Henig 2000, pp. 19–21.
  9. ↑ Henig 2000, p. 24.
  10. ↑ Hasan, Heather (2004). Mendel and The Laws Of Genetics. The Rosen Publishing Group. ISBN 9781404203099.
  11. 1 2 Henig 2000, pp. 47–62.
  12. 1 2 3 "The Mathematics of Inheritance". Online museum exhibition. The Masaryk University Mendel Museum. Archived from the original on 31 January 2013. Retrieved 20 January 2010.
  13. 1 2 3 "Online Museum Exhibition". The Masaryk University Mendel Museum. Archived from the original on 21 October 2014. Retrieved 20 January 2010.
  14. ↑ Windle, B.C.A. (1911). "Mendel, Mendelism". Catholic Encyclopedia. Looby, John (trans.). Retrieved 2 April 2007.
  15. 1 2 Carlson, Elof Axel (2004). "Doubts about Mendel's integrity are exaggerated". Mendel's Legacy. Cold Spring Harbor, NY: Cold Spring Harbor Laboratory Press. pp. 48–49. ISBN 978-0-87969-675-7.
  16. ↑ "Mendel's Garden". The Masaryk University Mendel Museum. Retrieved 20 January 2010.
  17. ↑ Henig 2000, pp. 78–80.
  18. ↑ Magner, Lois N. (2002). History of the Life Sciences (3, revised ed.). New York: Marcel Dekker, Inc. p. 380. ISBN 978-0-2039-1100-6.
  19. ↑ Gros, Franc̜ois (1992). The Gene Civilization (English Language ed.). New York: McGraw Hill. p. 28. ISBN 978-0-07-024963-9.
  20. ↑ Moore, Randy (2001). "The “Rediscovery” of Mendel’s Work" (PDF). Bioscene 27 (2): 13–24.
  21. ↑ Butler, John M. (2010). Fundamentals of Forensic DNA Typing. Burlington, MA: Elsevier/Academic Press. pp. 34–35. ISBN 978-0-08-096176-7.
  22. ↑ Henig 2000, pp. 134–138.
  23. ↑ Randy Moore (May 2001). "The "Rediscovery" of Mendel's Work" (PDF). Bioscene 27.
  24. ↑ Mendel, J.G. (1866). "Versuche über Pflanzenhybriden", Verhandlungen des naturforschenden Vereines in Brünn, Bd. IV für das Jahr, 1865, Abhandlungen: 3–47, . For the English translation, see: Druery, C.T.; Bateson, William (1901). "Experiments in plant hybridization" (PDF). Journal of the Royal Horticultural Society 26: 1–32. Retrieved 9 October 2009.
  25. ↑ Galton, D. J. (2011). "Did Mendel falsify his data?". QJM 105 (2): 215–216. doi:10.1093/qjmed/hcr195. PMID 22006558.
  26. ↑ Lorenzano, P (2011). "What would have happened if Darwin had known Mendel (or Mendel's work)?". History and Philosophy of the Life Sciences 33 (1): 3–49. PMID 21789954.
  27. ↑ Liu, Y (2005). "Darwin and Mendel: who was the pioneer of genetics?". Rivista di Biologia 98 (2): 305–22. PMID 16180199.
  28. ↑ Henig 2000, pp. 15–17.
  29. ↑ "The Enigma of Generation and the Rise of the Cell". The Masaryk University Mendel Museum. Retrieved 20 January 2010.
  30. ↑ Nogler, GA (2006). "The lesser-known Mendel: his experiments on Hieracium.". Genetics 172 (1): 1–6. PMC 1456139. PMID 16443600.
  31. ↑ Orel, Vítězslav; Rozman, Josef; Veselý, Vladimír (1965). Mendel as a Beekeeper. Moravian Museum. pp. 12–14.
  32. ↑ Demerec, M. (1956). Advances in Genetics. New York, N.Y.: Academic Press. p. 110. ISBN 978-0-0805-6795-2.
  33. ↑ Roberts, Michael; Ingram, Neil (2001). Biology (2 ed.). Cheltenham: Nelson Thornes. p. 277. ISBN 978-0-7487-6238-5.
  34. ↑ Matalova, A; Kabelka, A (1982). "The beehouse of Gregor Mendel". Casopis Moravskeho musea. Acta Musei Moraviae - Vedy prirodni. Car Morav Mus Acta Mus Vedy Prir 57: 207–212.
  35. ↑ Mayr E. (1982). The Growth of Biological Thought. Cambridge: The Belknap Press of Harvard University Press. p. 730. ISBN 0-674-36446-5.
  36. ↑ Henig 2000, pp. 1–9.
  37. ↑ Deichmann, Ute (2011). "Early 20th-century research at the interfaces of genetics, development, and evolution: Reflections on progress and dead ends". Developmental Biology 357 (1): 3–12. doi:10.1016/j.ydbio.2011.02.020. PMID 21392502.
  38. ↑ Elston, RC; Thompson, EA (2000). "A century of biometrical genetics". Biometrics 56 (3): 659–66. doi:10.1111/j.0006-341x.2000.00659.x. PMID 10985200.
  39. ↑ Pilpel, Avital (September 2007). "Statistics is not enough: revisiting Ronald A. Fisher’s critique (1936) of Mendel’s experimental results (1866)". Studies in History and Philosophy of Science Part C: Studies in History and Philosophy of Biological and Biomedical Sciences 38 (3): 618–626. doi:10.1016/j.shpsc.2007.06.009. PMID 17893069.
  40. ↑ Reid, J. B.; Ross, J. J. (2011). "Mendel's genes: toward a full molecular characterization". Genetics 189 (1): 3–10. doi:10.1534/genetics.111.132118. PMC 3176118. PMID 21908742.
  41. ↑ Ellis, T.H. Noel; Hofer, Julie M.I.; Timmerman-Vaughan, Gail M.; Coyne, Clarice J.; Hellens, Roger P. (2011). "Mendel, 150 years on". Trends in Plant Science 16 (11): 590–596. doi:10.1016/j.tplants.2011.06.006. PMID 21775188.
  42. ↑ Kutschera, Ulrich; Niklas, KarlJ. (2004). "The modern theory of biological evolution: an expanded synthesis". Naturwissenschaften 91 (6): 255–276. doi:10.1007/s00114-004-0515-y. PMID 15241603.
  43. ↑ Hall, Brian Keith; Hallgrímsson, Benedikt; Strickberger, Monroe W. (2014). Strickberger's evolution (5 ed.). Burlington, Mass.: Jones & Bartlett Learning. pp. 10–11. ISBN 978-1-4496-1484-3.
  44. 1 2 3 4 Fisher, R.A. (1936). "Has Mendel's work been rediscovered?" (PDF). Annals of Science 1 (2): 115–137. doi:10.1080/00033793600200111.
  45. ↑ Thompson, EA (1990). "R.A. Fisher's contributions to genetical statistics". Biometrics 46 (4): 905–14. doi:10.2307/2532436. PMID 2085639.
  46. ↑ Pilgrim, I (1984). "The too-good-to-be-true paradox and Gregor Mendel". The Journal of Heredity 75 (6): 501–502. PMID 6392413.
  47. ↑ Magnello, ME (1998). "Karl Pearson's mathematization of inheritance: from ancestral heredity to Mendelian genetics (1895-1909)". Annals of Science 55 (1): 35–94. doi:10.1080/00033799800200111. PMID 11619806.
  48. 1 2 Hartl, Daniel L.; Fairbanks, Daniel J. (2007). "Mud sticks: On the alleged falsification of Mendel's Data". Genetics 175 (3): 975–979. PMC 1840063. PMID 17384156.
  49. ↑ Piegorsch, WW (1990). "Fisher's contributions to genetics and heredity, with special emphasis on the Gregor Mendel controversy". Biometrics 46 (4): 915–924. doi:10.2307/2532437. PMID 2085640.
  50. ↑ Price, Michael (2010). "Sins against science: Data fabrication and other forms of scientific misconduct may be more prevalent than you think". Monitor on Psychology 41 (7): 44.
  51. ↑ Porteous, JW (2004). "We still fail to account for Mendel's observations.". Theoretical Biology & Medical Modelling 16 (1): 4. doi:10.1186/1742-4682-1-4. PMC 516238. PMID 15312231.
  52. ↑ Fairbanks, D. J.; Schaalje, G. B. (2007). "The tetrad-pollen model fails to explain the bias in Mendel's pea (Pisum sativum) experiments". Genetics 177 (4): 2531–2534. doi:10.1534/genetics.107.079970. PMC 2219470. PMID 18073445.
  53. ↑ Novitski, Charles E. (2004). "On Fisher's criticism of Mendel's results with the garden pea". Genetics 166 (3): 1133–1136. doi:10.1534/genetics.166.3.1133. PMC 1470775. PMID 15082533. Retrieved 20 March 2010. In conclusion, Fisher’s criticism of Mendel’s data—that Mendel was obtaining data too close to false expectations in the two sets of experiments involving the determination of segregation ratios—is undoubtedly unfounded
  54. ↑ Franklin, Allan; Edwards, AWF; Fairbanks, Daniel J; Hartl, Daniel L (2008). Ending the Mendel-Fisher controversy. Pittsburgh, PA: University of Pittsburgh Press. p. 67. ISBN 978-0-8229-4319-8.
  55. ↑ Monaghan, F; Corcos, A (1985). "Chi-square and Mendel's experiments: where's the bias?". The Journal of Heredity 76 (4): 307–309. PMID 4031468.
  56. ↑ Novitski, C. E. (2004). "Revision of Fisher's analysis of Mendel's garden pea experiments". Genetics 166 (3): 1139–1140. doi:10.1534/genetics.166.3.1139. PMC 1470784. PMID 15082535.

Bibliography

  • Smith, Jos A.; Cheryl Bardoe; Smith, Joseph A. (2006). Gregor Mendel: the friar who grew peas. Abrams Books for Young Readers. ISBN 0-8109-5475-3. 
  • William Bateson Mendel, Gregor; Bateson, William (2009). Mendel's Principles of Heredity: A Defence, with a Translation of Mendel's Original Papers on Hybridisation (Cambridge Library Collection – Life Sciences). Cambridge, UK: Cambridge University Press. ISBN 1-108-00613-2.  On-line Facsimile Edition: Electronic Scholarly Publishing, Prepared by Robert Robbins
  • Klein, Jan; Klein, Norman (2013). Solitude of a Humble Genius – Gregor Johann Mendel: Volume 1. Heidelberg: Springer. ISBN 978-3-642-35253-9. 
  • Henig, Robin Marantz (2000). The Monk in the Garden: The Lost and Found Genius of Gregor Mendel, the Father of Genetics. Boston: Houghton Mifflin. ISBN 978-0395-97765-1. 
  • Robert Lock, Recent Progress in the Study of Variation, Heredity and Evolution, London, 1906
  • Orel, Vítĕzslav (1996). Gregor Mendel: the first geneticist. Oxford [Oxfordshire]: Oxford University Press. ISBN 0-19-854774-9. 
  • Reginald Punnett, Mendelism, Cambridge, 1905
  • Curt Stern and Sherwood ER (1966) The Origin of Genetics.
  • Tudge, Colin (2000). In Mendel's footnotes: an introduction to the science and technologies of genes and genetics from the nineteenth century to the twenty-second. London: Vintage. ISBN 0-09-928875-3. 
  • Waerden, B. L. V. D. (1968). "Mendel's Experiments". Centaurus 12 (4): 275–288. doi:10.1111/j.1600-0498.1968.tb00098.x. PMID 4880928.  refutes allegations about "data smoothing"
  • James Walsh, Catholic Churchmen in Science, Philadelphia: Dolphin Press, 1906
  • Ronald A. Fisher, "Has Mendel's Work Been Rediscovered?" Annals of Science, Volume 1, (1936): 115–137. Discusses the possibility of fraud in his research.

Further reading

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