<prompt> Mytonic dystrophy is due to-Expansion in coding regionCAG triple nucleotide repeat mutationCTG triple nucleotide repeat mutationInvolves chromosome 15  <response>: Answer-C. CTG triple nucleotide repeat mutationMyotonic dystrophy is associated with a trinucleotide CTG repeat expansion on chromosome 19.This expansion affects the mRNA for the dystrophila myotonia protein kinase DMPK.Triple nucleotide repeat mutations Normally, a codon is triplet trinucleotide e.g. for CGG it is 5-50 and CGG triplet codon can be repeated, at a stretch, 5-50 times Non-coding region 