Rats are rodents, and their small size and rapid reproductive cycle makes them easy to maintain and breed in the laboratory. These factors have contributed to them becoming widely used laboratory animals, with over 8 million rats used in research worldwide. Both inbred and outbred strains of rat are available, although far fewer different strains in comparison to mice. The rat genome has been sequenced, and transgenic rats have been produced, although they are much less widely used than transgenic mice.
Basic biology and anatomy
Laboratory rats have been selectively bred from the brown Norway rat, (Rattus norvegicus) and retain many of the biological features of this wild rodent, although some morphological and behavioural differences are present (Stryjek et al 20121). Rats share common anatomical features with other terrestrial mammals, including humans, but have evolved some specific adaptations.