Hypothetical quantitative trait loci (QTL) for circadian period of locomotor activity in CXB recombinant inbred strains of mice

The locomotor activity of male mice (Mus musculus) of 13 CXB (BALB/cBy x C57BL/6J) recombinant inbred (RI) strains and their progenitor strains was monitored for 4 to 6 weeks by infrared photoelectric beams under constant dark. The circadian period (tau) of locomotor activity was calculated and used in quantitative trait locus (QTL analysis of strains' means. Results were compared with potential QTL found in a previous study of the BXD RI series. The mean tau of 13 CXB RI mouse strains (three to six animals per strain) in constant dark had a unimodal distribution suggesting polygenic inheritance. A number of potential QTL were found for this trait. There were two associations at p < .001, H23 on chromosome 3 and Pmv16 on chromosome 16. A region of chromosome 1 was associated with tau in both CXB and BXD RI series; There was also a conjunction with a locus determined from QTL analysis of the previously reported tau Of wheel running activity in seven CXB RI strains (Schwartz and Zimmerman, 1990).