A genetic chimerism or chimera (/kaɪˈmɪərə, kɪ-/ ky-MEER-ə, kih-) is a single organism composed of cells of different genotypes. Animal chimeras can be produced by the fusion of two (or more) embryos. In plants and some animal chimeras, mosaicism involvesdistinct types of tissue that originated from the same zygote, but differ due to mutation during ordinary cell division.
Normally, genetic chimerism is not visible on casual inspection; however, it has been detected in the course of proving parentage. More practically, in agronomy, "chimera" indicates a plant or portion of a plant whose tissues are made up of two or more types of cells with different genetic makeup; it can derive from a bud mutation or, more rarely, at the grafting point, from the concrescence of cells of the two bionts; in this case it is commonly referred to as a "graft hybrid", although it is not a hybrid in the genetic sense of "hybrid".
