analysis suggested that a dominant mutation on the D2 strain on distal mouse chromosome 12 was responsible for increased locomotor response to novelty (Figure 1A). As part of the phenotypic screening, B6D2*×B6 animals were weighed between the ages of 8 to 10 weeks, revealing a highly significant QTL for body weight in approximately the same location on distal mouse chromosome 12 (Figure 1B). Haplotype analysis indicated that heterozygous carriers (Mutant/+) of the distal 36.0 megabases (Mb) of the mutagenized chromosome 12 (between markers D12Mit158 and D12Mit263, see Figure 1A and Figure 2) were mildly hyperactive (Figure 1C) and weighed less (Figure 1D) than wild-type non-carriers.
