Myotonic dystrophy type 1 results from a trinucleotide CTG repeat expansion in the DMPK gene (Figure 6), encoding serine-threonine kinase, while myotonic dystrophy type 2 results from tetranucleotide CCTG repeat expansion in the CNBP (formerly ZNF9) gene, encoding nucleic acid-binding protein. The gene discussed is CNBP; the disease is myotonic dystrophy type 1.