human chimera

Typically seen in zoology (but also discovered to a rare extent in human beings), a chimera is an animal that has two or more different populations of genetically distinct cells that originated in different zygotes; if the different cells emerged from the same zygote, it is called a mosaicism. Chimerism in human beings has very few (about 40) reported cases. In biological research, chimeras are artificially produced by physically mixing cells from two different organisms. Chimeras are not hybrids, which form from the fusion of gametes from two species (like a donkey and a horse) that form a single zygote that will develop as much as it can (in this case into a live mule if the parents are jackass and mare, or a hinny if the parents are stallion and jenney); in comparison, chimeras are the physical mixing of cells from two independent zygotes: for example, one from the donkey and one from the horse. "Chimera" is a broad term and is often applied to many different types of mixing of cells from two different species.