Cytoplasmic inheritance is a property of genes present outside the nucleus and located in the mitochondria of animals, plants, and fungi, and in the chloroplasts of plant cells. Cytoplasmic inheritance is a non-Mendelian type of inheritance and is typically associated with the phenomenon of somatic segregation, where a cytoplasm containing mutant and wild type mitochondria (or chloroplasts) will hold only one a homologous population of these organelles after several cell divisions.

The first evidence for the presence of extranuclear genes was provided by the observation of variants of plants whose leaves are striped green and yellow because mutations in the chloroplasts of some cells result in the absence of chlorophyll and the green color. Mitochondria were later shown to exhibit cytoplasmic inheritance mainly through studies of mutants in yeast and other single-celled organisms. The most important evidence that mitochondria must contain their own genetic system was...