Genetic Polymorphism Study Of Y-SNP And Y-STR In The Wa, Bai, Dai Ethnic Groups Of Yunnan And Their Forensic Implications

Objective:DNA polymorphism on non-recombined region of Y chromosome(NRY) play an important role in forensic casework such as mix stain analysis, paternity cases where the putative father or other relatives are lacking and cases of suspect lacking because of its patrilineal inheritance. The single nucleotide polymorphisms with geographic specificity provide the possibility to predict ethincgeographic origin of biological samples who left in the crime scene, which can help to provide scent in investigative phase of a criminal procedure. In this study, the subject based on the unique genetic resources of Yunan Province, the Wa, Bai and Dai which are descendants of three distinct ancient tribe were chosen, and 7 Y-SNPs with high polymorphism in Eastern Asia and 17 Y-STRs including in Y filer kit were typed. The data of Y-SNP and Y-STR of the distribution characteristics in three ethnic groups were obtained, the relatedness of alleles distribution at Y-STR locus and its Y-SNP haplogroups background and the feasibility of ethnic origin predicted from Y-STR haplotype were primary discussion. All these may be useful for further study of Y chromosome DNA polymorphism in other ethnic groups and application on forensic science.Methods:Blood samples were collected from the Wa(n=100), Bai(n=146) and Dai(n=158), a total of 404 unrelated males were involved in this study. The genome DNA of 404 individuals were extracted with the phenol-chloroform method. All samples were typed using Nested amplified PCR and direct Sequencing methods with Y-SNP markers; 17 Y-STRs were typed using the AmpF/STR Yfiler system (Applied Biosystems). Data statistical analysis was used the software package Arlequin 3.5 and the program Network 4.1.5.6.Results:Of the seven Y-SNP haplogroups, O3-M122, O2-M95, K*-M9, C-M130 and F*-M89 were found in the Wa while O1-M119 and P*-M45 were absent; All seven Y-SNP haplogroups were observed in the Bai and six were found in Dai expect P*-M45 haplogroup. The frequency distribution of O3-M122 in the Wa, Bai and Dai was occupied in 56.0%,47.3%and 31.0%respectively; O2-M95 was occupied in 15.0%,15.8%and 39.9%respectively; K*-M9 was occupied in 24.0%,13.0%and 5.7%and C-M130 was occupied in 3.0%,10.2%and 5.7%, respectively.72,115 and 140 different 17-loci haplotypes were found in Wa, Bai and Dai samples, respectively; No haplotype was shared among the three groups. Wa appeared in lowest haplotype diversity (0.9875±0.0046) compared to Bai (0.9957±0.0015) and Dai (0.9981±0.0010) groups.In the Wa, high frequency distribution of alleles at 17 Y-STR loci was observed and showing striking difference between O3-M122 and O2-M95 haplogroups expect at DYS389Ⅱand DYS19; This difference was also found among O3-M122, O2-M95 and K*-M9 at DYS389 I, DYS19, DYS393, YGATAH4 and DYS438. Haplotype 15-12-23-29-15-15-12,17-12-10-11-22-13-13(14/12)-15-9-19 characterised in O3-M122 was sharply differ from haplotype 16-13-25-29-16-15-15,19-14-11-12-20-14-11-14-10-18 characterised in O2-M95. Alleles at most loci of the Bai showed moderate frequencies. In the Dai, the difference of high frequency distribution of alleles was observed between O3-M122 and O2-M95 at DYS389Ⅰ, DYS389Ⅱ, DYS19, DYS439, DYS392, DYS437, DYS438 and DYS448, and also observed among O3-M122, O3-M95 and O1-M119 at DYS390, DYS393 and DYS635.In the median jioning network which constructed using Y-STR haplotypes under the same Y-SNP haplogroup. The Wa presented nearly identical haplotypes and displayed star-like features in network of O3-M122, O2-M95 and K*-M9; Bai showed relatively high diversity of haplotype in the O3-M122 network expect partly haplotypes which situating at center of the network, and a small star-like features was also observed in the network of O2-M95; The Dai displayed star-like features and closely distributed with some of Bai samples in the O3-M122 network, and showed high haplotype diversity and relatively scattered in the O2-M95 network.Conclusions:In this study, the genetic data of Y-SNP and Y-STR in three ethnic groups were obtained, and the genetic charatistics of ethnic groups as well as explanation of the observed genetic differences amomg them were comparatively understood. Wa characterised in isolation ethnic and preserves a high level of patrilineal genetic diversity, and the allelic distribution at STR locus is strongly depend on its SNP haplogroups background which may have potential implications to predicte its Y-SNP haplogroup in forensic casework. In others, Dai and Bai revealed more intercommunion.