Myotonic dystrophy CTG repeats in an Italian population sample: evaluation of the polymorphism for forensic applications.

The myotonic dystrophy (DM) CTG repeat polymorphism has been studied in an Italian population sample. Polymerase chain reaction (PCR) amplification, manual polyacrylamide gel electrophoresis (PAGE), and silver staining were employed. Alleles were typed by comparison with a sequenced allelic ladder. A total of 25 different alleles, spanning the range from 5 to 31 CTG triplets, was observed. The heterozygosity was 79%, and no significant deviation from Hardy-Weinberg equilibrium was found. Eighty-one meioses from parentage testing were also analyzed, and a Mendelian pattern of inheritance was observed in all cases. In addition, we could successfully type the DM locus in 20 laboratory-prepared bloodstains, with 1 ng of DNA allowing clear definition of alleles. We conclude that the CTG repeats at the DM locus may be useful for forensic applications.