Austrian monk Gregor Mendel (1822–1884) was the founding father of modern genetics. His work with the garden pea, Pisum sativuum, was not consistent with the nineteenth-century ideas of inheritance. In his world, scientists believed that inheritance was essentially a mix of fluid that blended and passed from parents to children (see “blending theory” below).

Mendel was the first to demonstrate that distinct physical characteristics could be passed from generation to generation. In particular, Mendel studied peas of distinct and recognizable plant varieties; his experiments included the characteristics of height, flower color, pea color, pea shape, pod color, and the position of flowers on the stem. His theory was one called particulate inheritance, in which certain inherited characteristics were carried by what he called elementes, which eventually became the now well-known name “genes.”