Cleary et al. also mapped the activity of these origins in transgenic mice containing the ~45 kb DMPK locus from control (DM20, (CTG)~20•(CAG)~20) or DM1 (DM328, (CTG) > 300•(CAG) > 300) and found that only the origin downstream of the expanded (CTG) > 300•(CAG) > 300 TNR was active. This evidence concerns the gene DMPK and myotonic dystrophy type 1.