Massively parallel sequencing of short tandem repeats—Population data and mixture analysis results for the PowerSeq™ system

•Sequencing of STRs reveals substantial variation in addition to length variation.•Sequence variation of 17 STRs was assessed for three globally dispersed populations.•Stutter ratios of complex STR alleles with the same length can vary substantially.•Minor mixture contributions of 1% are recovered but are exceeded by stutters reads.•MPS STR analysis of minor mixture contributions down to 5% is routinely feasible.