Foundations of inbreeding The need for reproducible systems for
biomedical research on rats has led to the development of
various types of genetically standardized stocks. The first
inbred rat strain was developed in 1909; since then, hundreds of
others have been developed for many different physiological and
biochemical studies and to model different diseases. In some
cases, though, rat research is still done on outbred or random-
bred stocks. As described for mice, many of the same strategies
for creating genetically standardized rat resources have been
employed. Inbred sibling matings for 20 generations or more have
yielded hundreds of characterized strains. Strategies employed
by researchers inbred animals that have been out-crossed from
two separate inbred strains, and then maintained for
generations, are available and use. At the present time, there
are various larger recombinant inbred panels and some smaller
ones that researchers have used effectively for genetic mapping,
eQTL, and gene identification