Mendel's Pea Plants

Inheritance is discrete

First published: G. Mendel, "Versuche über Pflanzen-Hybriden", *Verhandlungen des naturforschenden Vereines in Brünn* 4 (1866): 3–47.

Cross tall and short pea plants; the next generation is all tall. Cross those; the generation after is tall and short in a 3:1 ratio. Inheritance is particulate.

Mendel cultivated tens of thousands of pea plants over eight years, tracking the inheritance of seven discrete traits (height, seed shape, seed colour, etc.). The data showed clear patterns: crossing pure-breeding tall and short plants produced all-tall first-generation hybrids; these in turn produced a second generation in approximately 3:1 tall-to-short ratio. The traits did not blend; they segregated. Mendel's explanation introduced what would later be called genes: discrete inherited factors, present in pairs, separating during gamete formation and recombining at fertilisation. The work was ignored for 34 years, rediscovered around 1900, and became the foundation of modern genetics. Philosophically, it established that the most basic carrier of biological information is discrete, not continuous — a result whose deepest implications were realised only with the molecular identification of DNA in the 1950s.