A QTL for the genetic variance in free-running period and level of locomotor activity between inbred strains of mice.

Many genes support the manifestation of the circadian period in mice. In a multiple-gene trait all genes contributing in a minor way to this characteristic are quantitative trait loci (QTL). Screens of both the BXD and the CXB panels of recombinant inbred mice suggested that distal chromosome 1, between 90 and 100 cM, contained a QTL, Cplaq3, for a difference in the circadian period of locomotor activity between the C57BL/6J and the DBA/2J and between the BALB/cBy and the C57BL/6By progenitor strains. The mice studied were a commercially available congenic strain, B6.D2-Mtv7a/Ty, from 50 to 100 days old. This congenic strain contains a small DBA/2J genomic insert that covers the region of the provisional QTL in a 99.9% C57BL/6J background. The congenic mice had a shorter period than C57BL/6J mice, confirming that this region has a QTL for the difference in period between the C57BL/6J and the DBA/2J strains. In addition, these data suggest that this region has a QTL for the mean amount of daily activity and for the pattern of locomotor activity.