Use of chimaeras to study development.

In Greek mythology a chimaera was a fire-breathing she-monster having a lion's head, a goat's body and a serpent's tail. Chimaeras have been used extensively as models for research in developmental biology under the more general definition of a composite animal or plant in which different cell populations are derived from more than one fertilized egg, or the union of more than two 2ametes (McLaren, 1976). This paper is limited to chimaeras produced by combination of cells from two or more mammalian embryos. Characteristics of chimaeras, methods for production and uses in research are described. Effort has been made to include results of direct relevance to domestic animals. Excellent reviews on mammalian chimaeras and their uses in research are available from McLaren (1976) and Le Douarin & McLaren (1984).