Congenic, Coisogenic and Segregating Inbred Strains

Abstract

Two isogenic (i.e. genetically identical) strains which differ only at a single locus (the differential locus) are known as ‘coisogenic’ strains. Such strains arise as a result of mutation within an inbred strain. Strains that approximate the coisogenic status can be developed by backcrossing a gene from a donor strain or stock into an inbred strain (the background strain or inbred partner), or by inbreeding with forced segregation at the locus in question. The resulting partially coisogenic strains, which differ at the differential locus and an associated segment of chromosome, are known as congenic strains. Congenic strains which differ at a histocompatibility locus have been called ‘congenic resistant’ strains, because they resist tissue and specific tumour transplants.