Gregor Mendel

Gregor Johann Mendel (1822 to 1884) was an Augustinian friar and scientist from Moravia, now in the Czech Republic, who discovered the basic rules of inheritance by breeding pea plants. He is often called the father of genetics, although his work was largely ignored until after his death.

Working at the abbey of St. Thomas in Brno between about 1856 and 1863, Mendel crossed thousands of pea plants and counted the offspring. He followed seven clear traits, such as round or wrinkled seeds and purple or white flowers. When he crossed plants with contrasting traits, one trait vanished in the first generation and reappeared in about one quarter of the second generation, a ratio of roughly 3 to 1.

He proposed that each trait is controlled by a pair of hereditary factors, now called alleles, one from each parent, that separate when gametes form and recombine at random. One factor can be dominant over another. His results are summarized in the principles of Mendelian genetics as the law of segregation and the law of independent assortment, though independent assortment holds only for genes that are not linked.

Mendel presented his results in 1865 and published them in 1866, but their statistical approach was unfamiliar to biologists and even Charles Darwin seems not to have known of them. In 1900 Hugo de Vries, Carl Correns and Erich von Tschermak independently reached similar conclusions and found his paper. Ronald Fisher later argued that Mendel's counts were closer to expectation than chance would predict, and the debate over this continues. Mendel's rules were joined with natural selection in the modern synthesis.

• Principles of Mendelian Genetics — the laws he described
• Allele — what he called hereditary factors
• Modern Synthesis — where his work joined evolution