Experiments on plant hybridization Mendel, known as the "father of modern genetics," chose to study variation in plants in his monastery's experimental garden. Mendel was assisted in his experimental design by Aleksander Zawadzki while his superior abbot
Napp wrote to discourage him, saying that the Bishop giggled when informed of the detailed genealogies of peas. After initial experiments with pea plants, Mendel settled on studying seven traits that seemed to be inherited 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. Between 1856 and 1863 Mendel cultivated and tested some 28,000 plants, the majority of which were
pea plants (
Pisum sativum). This study showed that, when true-breeding different varieties were crossed to each other (e.g., tall plants fertilized by short plants), in the second generation, one in four pea plants had
purebred recessive traits, two out of four were
hybrids, 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.
Initial reception of Mendel's work Mendel presented his paper, ("
Experiments on Plant Hybridization"), at two meetings of the Natural History Society of Brno in
Moravia on 8 February and 8 March 1865. It generated a few favorable reports in local newspapers, it was seen as essentially about hybridization rather than inheritance, had little impact, and was cited only about three times over the next thirty-five years. His paper was criticized then but is now considered a seminal work. Notably,
Charles Darwin was not aware of Mendel's paper, and it is envisaged that if he had been aware of it, genetics as it exists now might have taken hold much earlier. Mendel's scientific biography thus provides an example of the failure of obscure, highly original innovators to receive the attention they deserve.
Rediscovery of Mendel's work About forty scientists listened to Mendel's two groundbreaking lectures, but it would appear that they failed to understand the implications of his work. Later, he also carried on a correspondence with
Carl Nägeli, one of the leading biologists of the time, but Nägeli also failed to appreciate Mendel's discoveries. At times, Mendel must have entertained doubts about his work, but not always: "My time will come," he reportedly told a friend, During Mendel's lifetime, most biologists held the idea that all characteristics were passed to the next generation through
blending inheritance (indeed, many effectively are), in which the traits from each parent are averaged. 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 20th century that the importance of Mendel's ideas was realized. Though de Vries later lost interest in Mendelism, other biologists started to establish modern genetics as a science. All three of these researchers, each from a different country, published their rediscovery of Mendel's work within a two-month span in the spring of 1900. 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 had 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 20th century, with the biometricians claiming statistical and mathematical rigor, whereas the Mendelians claimed a better understanding of biology. Modern genetics shows that Mendelian heredity is, in fact, an inherently biological process, though not all genes of Mendel's experiments are yet understood. Ultimately, 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. In the
Soviet Union and the
People's Republic of China, Mendelian genetics was rejected in favor of
Lamarckism under the state policy of
Lysenkoism, leading to imprisonment and even execution of Mendelian geneticists as well as massive famines in both of those countries.
Modern analysis of the genes causing Mendel's pea phenotypes Mendel postulated that seven "factors" determine the features he studied in peas. These factors are called "
genes" today, but the nature of these genes remained mysterious for more than a century. The effort to identify these genes lasted until 2025 when the last 3 genes were discovered.
Other experiments Mendel also experimented with
hawkweed (
Hieracium). He published a report on his work with hawkweed, a group of plants of great interest to scientists at the time because of their diversity. However, the results of Mendel's inheritance study in hawkweeds were unlike those for peas; the first generation was very variable, and many of their offspring were identical to the maternal parent. In his correspondence with
Carl Nägeli he discussed his results but was unable to explain them. Mendel appears to have kept animals at the monastery, breeding bees in custom-designed
bee hives. None of his results on bees survived, except for a passing mention in the reports of the Moravian Apiculture Society. All that is known definitely is that he used Cyprian and Carniolan bees, 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. Mendel, on the other hand, was fond of his bees and referred to them as "my dearest little animals". After his death, Mendel's colleagues remembered that he bred mice, crossing varieties of different size, although Mendel has left no record of any such work. A persistent myth has developed that Mendel turned his attention to plants only after Napp declared it unseemly for a celibate priest to closely observe rodent sex. In a 2022 biography, Daniel Fairbanks argued that Napp could hardly have given such a pronouncement, as Napp personally oversaw sheep breeding on the monastery's extensive agricultural estate. Mendel also studied
astronomy and
meteorology, The majority of his published works were related to meteorology. == Mendelian paradox ==