MENDEL, GREGOR

MENDEL, GREGOR (1822–1884), Austrian monk and researcher on plant hybridization and heredity.

Gregor Mendel is widely regarded as the father of genetics because he laid the foundations of that science with his classic study of hybridization. Born on 22 July 1822 and christened Johann, the future Gregor Mendel was the first son of the peasant farmer, Anton, and his wife, Rosine née Schwirtlich. Growing up in rural Silesia in the village of Heinzendorf, and encouraged by the local priest, Father Johann Schreiber, young Mendel became familiar with the practical skills of the farmer, fruit grower, and beekeeper. Naturally the expectation was that he would one day take over the running of his father's farm. Then in 1833 the village schoolmaster, Thomas Makitta, advised sending Mendel away to the Piarist Central School in Leipnik. This set young Mendel on a different course. The next six years found Mendel in the gymnasium at Troppau.

To continue his studies, Mendel moved to Olmütz, where at the Philosophical Institute he entered the two-year program to prepare for entry to the university. Among his teachers was the mathematician, Johann Fux, and the physicist, Friedrich Franz. Unfortunately, his studies both at Troppau and at Olmütz were compromised by several breakdowns in his health, caused, it seems, by the stress of studying and tutoring to raise the needed funds for his education—needed because of the declining state of the family finances. In 1838 his father had suffered an accident that impaired his ability to run the farm, making it impossible for the family to send their son any support. Advised of the situation, Professor Franz suggested Mendel might consider becoming a candidate for the Augustinian Monastery of Saint Thomas in Brünn, Moravia. Mendel applied to join the order, a change of social status, he explained, determined by his need to be freed "from the bitter struggle for existence," (Orel, p. 44) that was involving him in exertions that he could no longer endure.

gregor the augustinian

We have no reason to doubt the sincerity of Mendel's support of the Christian religion, but clearly he would not have become a monk had his financial situation been different. Given the name "Gregor," he was to serve the monastery loyally, but as priest to the monastery parish he proved unsuited, for close encounters with the dying proved too much for him. Fortunately, the monastery had a teaching role in the schools and institutes in Moravia. Thus began Mendel's career as an unqualified adjunct teacher in 1849 at the Gymnasium in Znaim.

Qualification would involve an examination in Vienna. This he took in 1850, but failed. The remedy taken by Mendel's abbot, Cyrill Napp, was to send Mendel to Vienna University for four semesters from 1851 to 1853. Among his teachers were the physicist Christian Doppler and the botanist Franz Unger. The latter introduced him to the cell theory, the work of plant hybridists, and species transmutation.

Strangely, it was not until he was forced to retake the teacher qualification in 1855 that he returned to Vienna. Then the ordeal of the oral examination upset him so badly that he returned to the monastery seriously ill and unsuccessful. Fortunately, he was able to continue teaching as an unqualified adjunct at the newly established Modern School (Oberrealschule).

Mendel's teaching career came to an end in 1868 with his election as Cyrill Napp's successor as abbot. His new duties gave him little time for his research and his latter years were clouded by his dispute over the taxation of monasteries to support the state's religious fund. Only with his death on 6 January 1884, was this dispute resolved by his successor.

scientific research

Mendel's scientific interests were many, but for him there was no strict separation between fundamental and applied research. He was as concerned about the quality of the grape for wine making and the beauty of the fuchsia for decoration as he was for seeking an understanding of the nature of hybridization. Besides beekeeping, gardening—including the study of insect pests—and botanizing he was especially devoted to meteorological observation. His Vienna experience had taught him the value of experimental design, and the statistical character of the physical world. Speculation about species transformation, though couched in the language of the still popular Nature-philosophy (Naturphilosophie), brought into question the supposed fixity of species. Could the hybridization of existing forms have led to species multiplication? Equally, would an understanding of the nature of the hybridization process aid the breeders of animals and plants in their pursuit of commercially attractive varieties? Hybridization thus held out potential economic benefits and at the same time might reveal how novel combinations of characters are transmitted in heredity and new species formed. Following his return from Vienna University in 1853, he began to plan an experiment to address the question, for as he notes, "among the numerous experiments not one has been carried out to an extent or in a manner that would make it possible to determine the number of different forms in which hybrid progeny appear, permit classification of these forms in each generation with certainty, and ascertain their numerical relationships" (Stern and Sherwood, p. 2). This passage expresses the originality of his experimental design. The need for classification of hybrid progeny led him to choose hybridizations between forms differing in traits that "stand out clearly and decisively in the plants." The determination of numerical relations meant growing large populations and treating them in a statistical manner. In tracing descent from generation to generation he followed the individual traits rather than the old practice of treating the species as a whole.

By 1854 he had obtained thirty-four varieties of the garden pea (Pisum sativum) that he tested for constancy of type over a two-year period. Twenty-two of these he retained as controls, growing them for the duration of the experiments to confirm their constancy. Having selected clearly distinguished traits like plant height, for example—either six to seven feet or ¾ to 1 ½ feet—he arrived at the conception of "character pairs," seven of them in all. Some pairs, like round or wrinkled seeds, were characteristics of the embryo within its seed coat. Others, like the shape of the ripe pod—constricted or unconstricted—were characteristics of the grown plant.

Next he noted that in the hybrids yielded by crossing forms differing in each of the seven traits, only one of the contrasting expressions of each trait was expressed in the hybrid. Such characters he called "dominant." The hidden characters he called "recessive." When he grew the succeeding generation, however, the recessive characters reappeared, and the ratio between the numbers of dominants to recessives approximated to 3:1. Here was a statistical regularity holding for all seven traits. Breeding a further generation of offspring revealed to him the constitution of the dominant parents as one third pure-breeding and two-thirds hybrid. The ratio 3:1 in constitutional terms was really 1:2:1, reminding him of the terms in the binomial equation: (A + a)² =A² + 2Aa + a².

Mendel went on to show how several traits could be combined in the same hybridization, but each behaved separately from the others, yielding novel combinations of characters. Mendel interpreted his results as suggesting that hybrids form germ cells, the composition of which is representative of either the dominant or the recessive character. When therefore large numbers of the pollen and egg cells in a hybrid unite in fertilization all combinations of these cells are realized just as in the expansion of the binomial equation—hence the ratio 1:2:1, obscured by dominance as 3:1.

This study with the edible pea took Mendel from 1854 to 1863, after which he reviewed his analysis of the results and wrote the paper "Versuche über Pflanzen-Hybriden" (Experiments on plant hybrids), presenting the work in two lectures to the Natural Science Society (Naturforschender Verein) in Brünn on 8 February and 8 March 1865, and published in the Society's Proceedings (Verhandlungen) for that year.

aftermath

Nineteen citations of Mendel's paper of 1865 have so far been found in the literature of the nineteenth century. However, only one of these gave an adequate account of the paper and that was in a Russian doctoral dissertation. Of the 115 copies of the Proceedings sent out, fifty-four went to institutions that have been identified as recipients, but who read them we have no idea. While "obscure" may not be the appropriate word to describe this publication, well known or widely read it certainly was not. The one scientist who took Mendel's work seriously was Carl Wilhelm von Nägeli. Mendel's letters to him reveal the extent of his continuing hybridization research to seek the extent of validity of his theory of hybridization for other plant species. Also they speak to his search for hybrids in which there is no separation of the contrasted characters in germ cell formation, hence they would reproduce their like—be "constant hybrids." Such could be treated as new species. This interest led him to his very difficult and unresolved work on the hawkweeds (Hieracium). In this work Nägeli encouraged him, but contrary to the widely held view, Nägeli had not initiated this choice by Mendel.

Several issues concerning Mendel's contribution continue to be debated. Were his data too good to be true, as Ronald Fisher claimed in 1936? Franz Weiling has rejected this claim on the grounds that the situation in which germ cells are formed and fertilizations occur is not of the statistical character that Fisher assumed in his analysis. Fisher also expected there to be some misallocation of progeny to the class of pure dominants when in fact they were hybrid dominants. But he did not allow for ways in which despite the presence of dominance the two classes might be distinguished. There continues, too, to be disagreement over the context of Mendel's work. L. A. Callendar situates the work in the context of discussions of the origin of species. Vít?zslav Orel and Roger Wood have explored the economic circumstances in Moravia that caused attention to be focused on hybridization.

When in 1900 the three hybridists, Hugo de Vries, Carl Erich Correns, and Erich Tschermak von Seysenegg, perceived the ratio 3:1 in their own data, Mendel's work at last became widely known. It is appropriate that he is regarded as the founder of the science of genetics, although it is surely an exaggeration to claim the concept of the gene to be present in his paper of 1865.

See alsoDarwin, Charles; Science and Technology.

bibliography

Primary Sources

Mendel, Gregor. "Versuche über Pflanzen-Hybriden." Reprinted in Fundamenta Genetica: The Revised Edition of Mendel's Classic Paper with a Collection of Twenty-Seven Original Papers Published during the Rediscovery Era, edited by Jaroslav K?íženecký and Bohumil N?mec, 57–92. Brno, 1965.

Stern, Curt, and Eva R. Sherwood, eds. The Origin of Genetics: A Mendel Source Book. San Francisco and London, 1966.

Secondary Sources

Callender, L. A. "Gregor Mendel: An Opponent of Descent with Modification." History of Science 26 (1988): 41–75.

Fisher, Ronald A. "Has Mendel's Work Been Rediscovered?" Annals of Science 1 (1936): 115–137. Reprinted in Stern and Sherwood, 1966, pp. 139–172, see above.

Henig, Robin. The Monk in the Garden: The Lost and Found Genius of Gregor Mendel, the Father of Genetics. Boston, 2000.

Iltis, Hugo. Life of Mendel. London, 1932. 2nd impression, 1966. Abridged translation of Gregor Johann Mendel: Leben, Werk, und Wirkungl. Berlin, 1924.

Olby, Robert. Origins of Mendelism. 2nd ed. Chicago, 1985. Includes reprint of "Mendel no Mendelian?" History of Science 17 (1979): 53–72.

Orel, Vít?zslav. Gregor Mendel: The First Geneticist. Translated by Stephen Finn. Oxford, U.K., 1996.

Piegorsch, W. W. "The Gregor Mendel Controversy: Early Issues of Goodness of Fit and Recent Issues of Genetics." History of Science 24 (1986): 173–182.

Weiling, Franz. "Historical Study: Johann Gregor Mendel, 1822–1884." American Journal of Medical Genetics 40 (1991): 1–25.

Robert Olby