Mendelian and classical genetics

The modern science of genetics traces its roots to Gregor Johann Mendel, a German-Czech Augustinian monk and scientist who studied the nature of inheritance in plants. In his paper "Versuche über Pflanzenhybriden" ("Experiments on Plant Hybridization"), presented in 1865 to the Naturforschender Verein (Society for Research in Nature) in Brünn, Mendel traced the inheritance patterns of certain traits in pea plants and showed that they could be described mathematically.[6] Although this pattern of inheritance could only be observed for a few traits, Mendel's work suggested that heredity was both particulate, not acquired, and that the inheritance patterns of many traits could be explained through simple rules and ratios.

The importance of Mendel's work was not understood until early in the 1900s, after his death, when his research was re-discovered by other scientists working on similar problems. The word genetics itself was coined in 1905 by William Bateson, a proponent of Mendel's work. (The adjective genetic, derived from the Greek word genno (γεννώ): to give birth, predates the noun and was first used in a biological sense in 1860.) Bateson popularized the usage of the word genetics to describe the study of inheritance in his inaugural address to the Third International Conference on Plant Hybridization in London, England, in 1906.

After the rediscovery of Mendel's work, scientists tried to discover which molecules in the cell were responsible for inheritance. In 1910 Thomas Hunt Morgan argued that genes are on chromosomes, based on observations of a sex-linked white eye mutation in fruit flies. In 1913 his student Alfred Sturtevant used the phenomenon of genetic linkage to show that genes are arranged linearly on the chromosome.