GK and diabetes mellitus: Providing that diabetes in the GK stems from the selective isolation of diabetes susceptibility alleles present in an outbred colony of Wistar rats, genes involved in altered phenotypes in the BN.GK-Nidd/gk1 congenics may map to RNO1 regions that are genetically different between GK rats and either hypertensive SHR/SHRSP or WKY controls.