Forensic Applications Of A 41 Multi-InDel Panel And Genetic Dissection Of Yugu And Han Populations With Multiple DNA Markers

Background:Challenging DNA samples are frequently encountered in forensic practice.Detection and successful classification of challenging DNA samples are significant to the final identification and sentencing of unknown individuals(often criminal suspects)in cases.In addition,the traditional STR-based searching approach is getting into its deadlock due to the accumulation of new suspects.Use of limited DNA to obtain the related identity information,such as appearance,height,age,ancestry of the suspect tends to provide key clues for the investigations,which becomes one of the hotspots in the forensic DNA area.Identification,separation and scientific interpretation of mixed DNA is a common and extremely complex problem in daily forensic cases.The successful identification of mixed samples sometimes plays a key role in the detection of cases.Ancestry information inferred from a series of ancestry-informative molecular genetic markers can provide clues to narrow the scope of investigation of suspects and provide important evidence for judicial cases,which is also frequently studied in recent years.Studies have showed that the microhaplotype genetic marker can provide worthy information towards mixed DNA identification and ancestry inference.Multi-InDel genetic marker,composed of linked InDel loci within a short fragment in the human genome,have various potential application advantages of microhaplotypes and is compatible with the capillary electrophoresis(CE)platform in forensic DNA laboratory.It not only overcomes the defect of insufficient genetic polymorphism of single InDel locus,but also takes advantage of the short amplicon fragment suitable for detection of degraded DNA samples.In addition,by setting corresponding screening criteria to select Multi-InDel loci with relatively high Ae values and ancestry inference potency,a new solution to the identification and deconvolution of mixed DNA can be developed.It also provides the ancestral information of the samples,helps to narrow the investigation scope,and provides directional clues for the investigation of the case.Methods and contents:(1)Multi-InDels were systematically screened from the human genome and further testified;(2)The novel multiplex amplification system including the 41 autosomal Multi-InDel loci and one sex identifying gene(Amelogenin)was developed based on the CE platform and the five-color fluorescence labeling technology.According to the validation guidelines suggested by SWGDAM group,the novel system was systematically verified;(3)Population validations and investigations were carried out in the Han,Manchu and Mongolian groups using the previously developed typing system.The genetic polymorphisms of 41 Multi-InDel loci and their forensic efficacies were evaluated.Besides,genetic backgrounds of the three studied populations were explored by incorporating the population data from the 1000 Genomes Project;(4)Based on the next generation sequencing platform,we analyzed the genetic polymorphisms of STR(autosomal STR,Y-STR,X-STR),SNP(individual identification SNP,ancestry-informative SNP,phenotype-informative SNP)and mitochondrial DNA hypervariable region sequences and their forensic application efficiency in Han and Yugu groups.The genetic backgrounds of Han population and Yugu ethnic group were analyzed from multiple DNA markers.Results and Conclusions:(1)The 41 Multi-InDel loci showed high cumulative discrimination power in different populations.In addition,the results of Ae,In value and STRUCTURE genetic analysis showed that 41 Multi-InDel loci could identify mixed DNA sample and providing valuable ancestry information;(2)The 41 MultiInDel system was proved to be highly sensitive,stabile and specific to human DNA.It could become the promising tool for degraded samples and mixed samples;(3)It was confirmed that the 41 Multi-InDel has high forensic efficiency in Manchu and Mongolian ethnic minorities and the Han population.The system can be used as an effective tool for personal identification and kinship determination and can be easily promoted and applied in forensic DNA laboratory.Besides,it was also revealed that Han,Manchu and Mongolian groups have close genetic relationships with CHB population,and the Han population and Manchu group shared more similar genetic composition;(4)The NGS-based typing system which incorporating multiple genetic markers showed high forensic application efficiency in Han and Yugu.From the perspective different DNA markers,it was demonstrated that the genetic background of Yugu group was similar to that of northern Han populations.