Gregor Mendel and his peas – the origin of modern genetics

Bob Harveson – University of Nebraska – Lincoln Extension Plant Pathologist

This is part of a series celebrating the International Year of Pulses.

International Year of the Pulse

Peas have been cultivated for thousands of years and archeological evidence suggests they were a regular companion with wheat and barley. This crop’s origin is thought to be the same as that of the cereals, being native to the Fertile Crescent, an area of the Middle East stretching from the Persian Gulf, through modern-day southern Iraq, Syria, Lebanon, Jordan, Israel, and northern Egypt.

While the crop may be ancient, it has played a pivotal role in the creation and development of the modern science of genetics.

The Agricultural Monk

Gregor Johann Mendel was a person of German ancestry living as a monk in Brno, Moravia (present-day Czech Republic). He was educated at the University of Vienna in Austria and conducted experiments between 1856 and 1863 utilizing garden peas within a small five-acre plot on the monastery grounds of the Abbey of St. Thomas.

Mendel worked with seven distinct characteristics of pea plants: plant height, pod shape and color, seed shape and color, and flower position and color. He carefully sorted the progeny derived from the parent plants based on these characteristics and counted the number that inherited each character. As a result of these studies, he discovered that these heritable traits were passed on by the parents and were distributed among the resulting offspring in definitive mathematical ratios, which established specific laws of inheritance for the first time. For example, with seed color, he showed that when a yellow pea and a green pea were cross pollinated, the resulting offspring plant always produced yellow seeds. However, in the next generation of plants, the green peas reappeared at a ratio of 1:3 (green to yellow). These studies also recognized that some traits were dominant while others were recessive. This example shows that yellow was the dominant trait.

The Forgotten Birth of Modern Genetics

Although Mendel’s work was largely accurate, his ideas were never recognized by his peers during his lifetime (1822-1884). His findings were originally published in an obscure Austrian journal in 1866. He died in obscurity and his work went unnoticed until being rediscovered around 1900 by four scientists: the Dutch botanist Hugo de Vries, the German botanist and geneticist Carl Correns, the Austian agronomist Erich von Tschermak-Seysenegg (as a graduate student), and the American wheat breeder and agricultural economist William Jasper Spillman.

Farmers had known for centuries that crossbreeding animals or plants could favor certain desirable traits. As the 20th century dawned, these empirical observations could now be explained scientifically on the basis of the newly discovered ideas of Mendelian genetics. Mendel’s pea plant experiments established many of the rules of heredity, now referred to as the laws of Mendelian inheritance, which helped stimulate the rapid advances in genetics and plant breeding of the last century.

About Robert Wright

Robert Wright is a Professor and Extension Entomologist at University of Nebraska-Lincoln. You can reach him by email at rwright2@unl.edu. Follow him on Twitter @BobWrightUNL
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