Canine BAC clone contigs encompassing the Hcrtr2 locus (A) and Hcrt (B). Approximate exon locations are indicated by dark boxes with associated exon numbers. Sequence tag sites (STS) for which locations were not strictly constrained were spaced at roughly equidistant intervals between constrained markers. Polymorphic microsatellite markers are indicated with dotted lines. Note the large distance between exons 1 and 2 as well as between exons 4 and 5. The crossover reported in Figure 3 occurred between 6-28-2 and exon 5.