Genetic or heredity science is a branch of biology that examines the inheritance and diversity of organisms. Turkish in the German last genetic word in 1831 Greek γενετικός - genetikos ( "genitive") was derived from the word. The origin of this word is based on the word kökenνεσι gen - genesis. With the awareness that the characteristics of living beings are hereditary, plants and animals have been rehabilitated since prehistoric times. However, modern genetic science, which seeks to understand hereditary transmission mechanisms, began only in the mid-19th century with the work of Gregor Mendel. Mendel did not know the physical basis of heredity, he observed that these traits were transferred in a discrete manner; Nowadays these inheritance units are called " genes ".