Mendel

Gregor Johann Mendel (1822–1884) was an Austrian monk, botanist, and scientist who established the basic laws of heredity. Working in the monastery garden in Brno, he studied how traits are passed from one generation to the next, applying careful observation and quantitative analysis to his data.

Mendel studied the pea plant (Pisum sativum) because it has clear, distinguishable traits, short generation times, and the ability to control pollination. He conducted hundreds of crosses, removing anthers to prevent self-pollination and manually pollinating flowers. He followed true-breeding varieties across several generations to track how characteristics appeared and reappeared.

From these experiments he proposed two core principles. The law of segregation states that organisms possess pairs of hereditary factors (now called genes) that separate during gamete formation, so offspring inherit one factor from each parent. The law of independent assortment posits that the distribution of factors for different traits is independent in the offspring, for unlinked traits. Mendel also observed dominant and recessive traits, evidenced by predictable phenotypic ratios such as 3:1 in monohybrid crosses and 9:3:3:1 in dihybrid crosses.

Mendel published Experiments on Plant Hybridization in 1866, but his work attracted little attention during his lifetime. It was rediscovered in 1900 by Hugo de Vries, Carl Correns, and Erich von Tschermak, who independently confirmed his results. His methods and conclusions laid the groundwork for classical genetics and the concept of particulate inheritance.

Mendel’s legacy endures as the founder of genetics. While many traits follow simple Mendelian patterns, others involve more complex inheritance, including polygenic, linked, or non-Mendelian modes. His quantitative approach influenced the development of modern biology.