Mytonic dystrophy is due to-

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