Segregation of genetic determinants for murine glucuronidase synthesis and loss in CXB recombinant-inbred strains.

A set of recombinant-inbred strains developed from mouse strains BALB/c and C57BL/6 includes two beta-glucuronidase phenotypes that are not seen in either of the progenitor strains. These new recombinant phenotypes indicate that glucuronidase levels are regulated by genes additional to the Gur locus, which is closely linked to the glucuronidase structural gene (Gus) and is known to regulate the rate of glucuronidase synthesis. In this study, induced rates of glucuronidase synthesis were determined for these recombinant-inbred strains, and rate constants for enzyme loss were calculated. The rate of synthesis was found to segregate with the Gus gene in all of the strains, and only the determinants for rate of enzyme loss recombined to give new phenotypes. It was concluded that at least two genes affect the rate of enzyme loss, that these genes are not closely linked to each other or to the Gur-Gus region on chromosome 5, and that no major determinants of glucuronidase synthesis segregate independently of Gur.