Mendel'S Law

Part of speech: noun (n.)

A principle governing the inheritance of many characters in animals and plants, discovered by Gregor J. Mendel (Austrian Augustinian abbot, 1822-84) in breeding experiments with peas. He showed that the height, color, and other characters depend on the presence of determinating factors behaving as units. In any given germ cell each of these is either present or absent. The following example (using letters as symbols of the determining factors and hence also of the individuals possessing them) shows the operation of the law: Tallness being due to a factor T, a tall plant, arising by the union in fertilization of two germ cells both bearing this factor, is TT; a dwarf, being without T, is tt. Crossing these, crossbreeds, Tt, result (called generation F1). In the formation of the germ cells of these crossbreeds a process of segregation occurs such that germ cells, whether male or female, are produced of two kinds, T and t, in equal numbers. The T cells bear the factor "tallness," the t cells are devoid of it. The offspring, generation F2, which arise from the chance union of these germ cells in pairs, according to the law of probability, are therefore on an average in the following proportions: