Close_up of fruit flies Drosophila melanogaster feeding on fruit. D. melanogaster is a small, common fly. It has been in use for over a century to study genetics and lends itself well to behavioral studies. Thomas Hunt Morgan was the preeminent biologist studying Drosophila early in the 1900磗. Morgan was the first to discover sex_linkage and genetic recombination, which placed the small fly in the forefront of genetic research. Due to its small size, ease of culture and short generation time, geneticists have been using Drosophila ever since. It is one of the few organisms whose entire genome is known and many genes have been identified.