GREGOR MENDEL, 'VERSUCHE ÜBER PLFLANZENHYBRIDEN'

Gregor Mendel

Today, The Grandma was preparing her salad when se has realized it has got some peas. She doesn't like peas but, suddenly, she has remembered Gregor Johann Mendel, the Austrian scientist who experimented with peas and established many of the rules of heredity, rules that we know as the laws of Mendelian inheritance, the origin of DNA studies.

The Grandma has decided to search in Internet more information about Gregor Mendel and his rules who was born on a day like today in 1822.

Gregor Johann Mendel (20 July 1822-6 January 1884) was a scientist, Augustinian friar and abbot of St. Thomas' Abbey in Brno, Margraviate of Moravia.

Mendel was born in a German-speaking family in the Silesian part of the Austrian Empire, today's Czech Republic, and gained posthumous recognition as the founder of the modern science of genetics. Though farmers had known for millennia 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.

Mendel worked with seven characteristics of pea plants: plant height, pod shape and color, seed shape and color, and flower position and color.

More information: BBC

Taking seed color as an example, Mendel showed that when a true-breeding yellow pea and a true-breeding green pea were cross-bred their offspring always produced yellow seeds. However, in the next generation, the green peas reappeared at a ratio of 1 green to 3 yellow. To explain this phenomenon, Mendel coined the terms recessive and dominant in reference to certain traits. 

In the preceding example, the green trait, which seems to have vanished in the first filial generation, is recessive and the yellow is dominant. He published his work in 1866, demonstrating the actions of invisible factors, now called genes, in predictably determining the traits of an organism.

Gregor Mendel

The profound significance of Mendel's work was not recognized until the turn of the 20th century, more than three decades later, with the rediscovery of his laws.

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.

Mendel was born into a German-speaking family in Hynčice, Heinzendorf bei Odrau in German, at the Moravian-Silesian border, Austrian Empire, now a part of the Czech Republic.

He was the son of Anton and Rosine 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, the house where Mendel was born is now a museum devoted to Mendel.

During his childhood, Mendel worked as a gardener and studied beekeeping. 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.

More info: How Mendel's pea plants helped us understand genetics

He became a friar in part because it enabled him to obtain an education without having to pay for it himself. As the son of a struggling farmer, the monastic life, in his words, spared him the perpetual anxiety about a means of livelihood. He was given the name Gregor, Řehoř in Czech, when he joined the Augustinian friars.

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. 

Gregor Mendel

Upon recommendation of his physics teacher Friedrich Franz, 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. At Vienna, his professor of physics was Christian Doppler. 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. In 1867, he replaced Napp as abbot of the monastery.

After he was elevated as abbot in 1868, his scientific work largely ended, as Mendel became overburdened with administrative responsibilities, especially a dispute with the civil government over its attempt to impose special taxes on religious institutions.

More information: Khan Academy

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.

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 to carry out a study in the monastery's 2 hectares experimental garden, which was originally planted by Napp in 1830. Unlike Nestler, who studied hereditary traits in sheep, Mendel used the common edible pea and started his experiments in 1856.

Gregor Mendel with fellow Monks, 1848

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, 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.

More information: The Human Genome

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. It generated a few favorable reports in local newspapers, but was ignored by the scientific community.

When Mendel's paper was published in 1866 in Verhandlungen des naturforschenden Vereines in Brünn, it was seen as essentially about hybridization rather than inheritance, had little impact, and was only cited about three times over the next thirty-five years. His paper was criticized at the time, 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.

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. Mendel also bred bees in a bee house that was built for him, using bee hives that he designed. He also studied astronomy and meteorology, founding the Austrian Meteorological Society in 1865. The majority of his published works was related to meteorology.

Gregor Mendel's Peas

Mendel also experimented with hawkweed (Hieracium) and honeybees. 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 was unlike his results 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. It was not appreciated until the end of the nineteen century that many hawkweed species were apomictic, producing most of their seeds through an asexual process.

More information: Science Learning Hub

None of his results on bees survived, except for a passing mention in the reports of 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.

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

During Mendel's 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. 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.

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.

More information: Nature

The value and utility of any experiment are determined 

by the fitness of the material to the purpose for which it is used,

and thus in the case before us it cannot be immaterial

what plants are subjected to experiment and in what manner

such experiment is conducted.

Gregor Mendel