Massively parallel sequencing (MPS) has rapidly become a promising method for forensic DNA typing, due to its ability to detect a large number of markers and samples simultaneously in a single reaction, and sequence information can be obtained directly. In the present study, two kinds of forensic genetic markers, short tandem repeat (STR) and identity-informative single nucleotide polymorphism (iiSNP) were analyzed simultaneously using ForenSeq DNA Signature Prep Kit, a commercially available kit on MPS platform. A total of 152 DNA markers, including 27 autosomal STR (A-STR) loci, 24 Y chromosomal STR (Y-STR) loci, 7 X chromosomal STR (X-STR) loci and 94 iiSNP loci were genotyped for 107 Tibetan individuals (53 males and 54 females). Compared with length-based STR typing methods, 112 more A-STR alleles, 41 more Y-STR alleles, and 24 more X-STR alleles were observed at 17 A-STRs, 9 Y-STRs, and 5 X-STRs using sequence-based approaches. Thirty-nine novel sequence variations were observed at 20 STR loci. When the flanking regions were also analyzed in addition to target SNPs at the 94 iiSNPs, 38 more alleles were identified. Our study provided an adequate genotype and frequencies data of the two types of genetic markers for forensic practice. Moreover, we also proved that this panel is highly polymorphic and informative in Tibetan population, and should be efficient in forensic kinship testing and personal identification cases. Several genetic markers have been introduced to forensic genetics to clarify the problems of kinship analysis and personal identification. Short tandem repeats (STRs) and single nucleotide polymorphisms (SNPs) are commonly used genetic markers in present forensic cases 1,2. STRs, usually 2-6 bp in length, are commonly typed with the amplified fragment length polymorphism (Amp-FLP) strategy combining fluorescently labelled multiplex PCR and capillary electrophoresis (CE) 3. Allele calling can thus be inferred from fragment length by comparison with a locus specific allelic ladder that has been previously sequenced, where the number of repeat units is distinct 2. Thus, each allele is regarded as a lengthbased (LB) allele using this approach. With the advancement of sequencing technologies over the last decade, the existence of sequence structure variations in alleles with the same length has been uncovered 4. SNPs, which could be amplified with smaller amplicons, are bi-allelic genetic markers with lower mutation rates compared with STRs 5. Several autosomal SNP marker sets and detection methods, such as single-base extension, chip-based microarrays, and allele-specific hybridization arrays, have been developed to compensate for the relatively weaker discrimination power of single loci caused by the bi-allelic nature of the human genome 5-7. However, these methods are not widely used in forensic practice due to the requirement of higher DNA inputs or the limited ability to detect a vast number of SNP loci in a single reaction 8. Different from detection methods mentioned above, massively paralle...
