Rediscovery of Mendel’s Hereditary Theory Summary

  • Last updated on November 10, 2022

By 1899, Gregor Mendel had been dead some fifteen years, his notebooks were mostly destroyed, and his work was forgotten. The independent rediscovery of Mendel’s work by three scientists and the controversies associated with priority between them led to a reexamination of Mendel’s role in science, as well as launching the modern science of genetics.

Summary of Event

The Austrian monk Gregor Mendel is generally considered to be the founder of modern genetics. During the period between 1854 and 1863, he carried out an extensive series of fertilization experiments, utilizing the common garden pea (genus Pisum), in which he observed the appearance or disappearance of various traits. Based upon the ratios in which these traits appeared among the plant’s offspring, Mendel established what later became known as Mendel’s laws of heredity. In 1865, Mendel presented the results of this work before the Brünn (Brno) Natural Science Society. In 1866, his results were published in the relatively obscure scientific journal of the society, Proceedings of the Brünn Society for the Study of Natural Science. Genetics;laws of heredity Mendel, Gregor Chromosomes;and heredity[Heredity] Correns, Carl Erich [kw]Rediscovery of Mendel’s Hereditary Theory (1899-1900) [kw]Mendel’s Hereditary Theory, Rediscovery of (1899-1900) [kw]Hereditary Theory, Rediscovery of Mendel’s (1899-1900) [kw]Theory, Rediscovery of Mendel’s Hereditary (1899-1900) Genetics;laws of heredity Mendel, Gregor Chromosomes;and heredity[Heredity] Correns, Carl Erich [g]Europe;1899-1900: Rediscovery of Mendel’s Hereditary Theory[6370] [c]Genetics;1899-1900: Rediscovery of Mendel’s Hereditary Theory[6370] [c]Science and technology;1899-1900: Rediscovery of Mendel’s Hereditary Theory[6370] Bateson, William Seysenegg, Erich Tschermak von Vries, Hugo de Weldon, Walter

Mendel’s first law became known in the early twentieth century as the law of segregation, in which genetic factors (merkmal) become segregated during the formation of gametes. The second law, the law of independent assortment, reflected his observations that traits often segregated independently of each other. That is, the appearance of a given trait, such as purple flowers, did not affect the probability of the appearance of another trait, such as wrinkled seeds, in the same plant.

The rediscovery of Mendel’s work some fifteen years after his death also led to the belief that a combination of factors had resulted in the undeserved if temporary obscurity of that work. These factors included his amateur status in a profession dominated by professional scientists, his presentation and publication in an obscure venue, and even the difficulty of understanding Mendel’s use of statistics. Analysis by authors Randy Moore and Robin Henig has suggested it is more likely that his work was simply not considered groundbreaking at the time. As noted by Moore, Mendel’s work had appeared in numerous journals and other publications in the years after the initial presentation.

Gregor Mendel.

(Library of Congress)

Three individuals are credited with the independent rediscovery of Mendel: Erich Tschermak von Seysenegg, Seysenegg, Erich Tschermak von a young Austrian graduate student preparing his thesis; Carl Erich Correns, a German botanist; and Hugo de Vries Vries, Hugo de , a Dutch botanist. Once it became clear that each had independently cited Mendel’s work, the question of priority for the rediscovery, particularly between Correns and de Vries, brought those earlier studies to prominence.

Seysenegg published his doctoral thesis in 1900. Included in his summary was a reference to the earlier work of Mendel, work that he argued was confirmed in his own experiments. Both Moore and Henig point out, however, that Seysenegg never recognized the hereditary principles, Mendel’s laws, in the summary of his own work, nor did he understand the significance of the ratios Mendel had reported. It is possible that Seysenegg was aware of Mendel’s studies prior to beginning his thesis; his grandfather, Eduard Frenzl, was an Austrian botanist who had feuded with Mendel during the 1850’s. Seysenegg’s later membership in the Nazi Party and support for eugenics further damaged the credibility of claims to have rediscovered Mendel.

Claims for rediscovery exhibit greater credence in the work by Correns and de Vries. By 1900, De Vries was a highly respected Dutch botanist who had once published his own theory of heredity, emphasizing characters he called “pangenes.” In March, 1900, de Vries Vries, Hugo de presented a paper before the Dutch Academy of Science in which he described the appearance of traits in ratios similar to those previously reported by Mendel. Shortly afterward, de Vries published his work and sent a copy of the paper to Correns. While it remains unclear whether de Vries fully understood the significance of the work of Mendel that he had confirmed, his claim to rediscovery stands on firmer ground than does that of Seysenegg.

By the time Correns received a copy of de Vries’ paper, he was already familiar with Mendel’s work. In fact, he had cited it in an 1899 publication. Correns further noted the importance of the nucleus in the segregation of genetic “factors” (anlage). While one could dispute whether the others fully understood the significance of Mendel’s ratios, there is no question that Correns did. Correns’s use of the term anlage in place of Mendel’s merkmal is evidence of his understanding. Correns argued that a characteristic or trait is determined by its own anlage, a principle close to the modern idea of a gene. He also suggested individual anlage may be either dominant or recessive.

In his presentation of specific ratios such as the 9:3:3:1 ratio observed in certain dihybrid crosses, Correns reported data that are now often incorrectly attributed to Mendel. Correns provided an explanation for the specific ratios of traits observed in offspring by both Mendel and himself—albeit an abstract explanation in principle. He also explained that anlage segregate during meiosis and that cell division results in the formation of gametes. His claim to have rediscovered Mendel’s work and understood its signficance is borne out by the fact that he named the abstract cause behind the trait ratios he observed “Mendel’s principle.”

William Bateson Bateson, William , a zoologist at Cambridge University who learned of Mendel’s work by reading the publications of Correns and de Vries Vries, Hugo de , is credited with being among the first to disseminate Mendel’s principles. In a lecture before the Royal Horticultural Society at Liverpool in May, 1900, Bateson used Mendel’s principles to explain his own investigations. Bateson coined the term “genetics” when applying Mendel’s principles to the animal kingdom. He later became the first professor of genetics at Cambridge.

This is not to say that all scientists were in complete agreement with Mendel’s observations. Walter Weldon Weldon, Walter , one of Great Britain’s leading statisticians, argued vociferously that other explanations were possible in analyzing Mendel’s work. For example, he believed that traits were never lost, but were merely masked (so that it would be possible in principle for any parents to have offspring with any traits). Nevertheless, the ability of others to reproduce Mendel’s ratios eventually convinced most skeptics of the “amateur’s” accuracy and conclusions.

Significance

The rediscovery of Mendel’s laws brought to the forefront the nascent field of modern genetics. In addition to forming the basis for the terminology that remains instrumental in understanding the field, terminology largely invented by Bateson Bateson, William , the recognition of Mendel’s laws of heredity led to the appreciation of the man himself, whose work had been largely forgotten. It is easily overlooked that at the time of the rediscovery, the genetic basis for Mendel’s laws was unclear. Chromosomes had been observed by Karl Nageli in the 1840’s, but it was only after Walter Sutton—a student at Columbia University in the first years of the twentieth century—observed the pairing and subsequent separation of chromosomes during cell division that the physical explanation for Mendel’s laws became apparent.

In retrospect, even if Mendel’s work had not reappeared, somebody else would probably have carried out similar work with similar conclusions. Indeed, Correns did exactly that. Mendel was fortunate in choosing plants that would self-pollinate and, more important, tracking traits that we now know to be encoded on different chromosomes. In this respect, the work of a “later Mendel” might not have resulted in reliable interpretations as quickly as Mendel’s work did. At any rate, Mendel’s work was rediscovered, and its rediscovery formed the foundation upon which the field of genetics advanced during the new century.

Further Reading
  • citation-type="booksimple"

    xlink:type="simple">Edelson, Edward. Gregor Mendel and the Roots of Genetics. New York: Oxford University Press, 2001. Popular account of Mendel’s life and works. Included are controversies dealing with validity of his statistics.
  • citation-type="booksimple"

    xlink:type="simple">Henig, Robin. The Monk in the Garden. New York: Houghton Mifflin, 2000. Well-researched biography of the man considered to be the modern founder of genetics.
  • citation-type="booksimple"

    xlink:type="simple">Moore, Randy. “The Rediscovery of Mendel’s Work.” Bioscene 27 (2001): 13-24. As noted by the author, Mendel’s work was not considered groundbreaking in its time. The controversies associated with priority of rediscovery played a significant role in reinterpreting the significance of Mendel’s laws.
  • citation-type="booksimple"

    xlink:type="simple">Raven, Peter, et al. Biology. 7th ed. Boston: McGraw-Hill, 2005. College textbook that provides extensive discussion of Mendel’s work and his laws of heredity. Illustrations include summary diagrams, as well as images reproduced from Mendel’s notebook.
  • citation-type="booksimple"

    xlink:type="simple">Stomps, T. “On the Rediscovery of Mendel’s Work by Hugo de Vries.” Journal of Heredity 45 (1954): 293-294. Discusses the controversial role of one of the alleged codiscoverers of Mendel.
  • citation-type="booksimple"

    xlink:type="simple">Waller, John. Einstein’s Luck: The Truth Behind Some of the Greatest Scientific Discoveries. New York: Oxford University Press, 2002. Addresses the myths behind scientific achievements. The section about Mendel presents questions about why he was largely ignored by the scientific community during his lifetime.

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