Several years later, in 1992, studies revealed that the gene defect responsible for DM1 was the expansion of a CTG repeat in the 3’ untranslated region of DMPK (Dystrophia Myotonica-Protein Kinase) gene, located on the long arm of chromosome 19 (chr19q13.3) (OMIM #605377) [26–28]. Here, DMPK is linked to myotonic dystrophy type 1.