Electrophoretic Mobility of Amplified Products at MCT118 Locus.

DNA typing of MCT118 (D1S80) locus has been performed with polyacrylamide gel electrophoresis using D1S80 allelic ladder. However, some oŠ-ladder variants, which showed diŠerent electrophoretic mobility compared with the allelic ladder, were observed frequently in MCT118 typing. Five variants from ˆve previously typed individuals were selected for sequence analysis. The sequence of the variants were determined to ascertain whether sequence variation or size variation is the cause of altered migration of the oŠ-ladder variants. All of the variants have nucleotide substitutions resulting in diŠerent sequences of some repeat units and do not have insertions or deletions. Consequently, the MCT118 allelic polymorphism is due to variation in the number of repeat units and to sequence variation among repeats. Furthermore, we examined electrophoresis conditions in order to accurately determine the type of MCT118. Under suitable electrophoresis conditions, all of the variants were typed as corresponding alleles within ±0.15 repeats.