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

Recombinant inbred animals that have been out-crossed from two separate inbred strains, and then maintained for generations, are available and in 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 studies.  A wide variety of behavioral, cardiovascular, metabolic, inflammatory, and other traits are already mapped, and other projects are underway. 

Consomic panels--in which an entire chromosome from one inbred strain replaces the corresponding chromosome in another inbred strain, and vice versa, are being generated. From the consomic strains, researchers can rapidly breed congenic strains that carry only a small segment that differs between animals to narrow the region on a chromosome to a size that can be targeted for gene identification. The success of this strategy for advancing cancer research has already been realized for a rat model of mammary carcinogenesis.

Technical aspects

For additional details on the process of generating inbred rats, explore the Generating Inbred Rats area of this site.