Objective To investigate the application value of the MHSeqTyper47 kit in kinship identification.Methods Multiplexed amplification and library preparation were performed for DNA samples from 113 related individuals by using the MHSeqTyper47 kit.The libraries were sequenced on a MiSeq FGx sequencer,and the data were analyzed using MHTyper for microhaplotype genotyping.The kinship indexes were calculated to evaluate the application efficiency of this kit in kinship identification and compared with those of the GlobalFilerTM kit.Results For the MHSeqTyper47 kit,the CPI values in trio identification were 1.43× 1011～6.15×1018.The CPI values in duo identification were 1.02× 105～1.53× 1013.The CFSI values in full sibling identification were 7.73×101～2.59×1016.Trios,duos and full siblings could be completely distinguished from unrelated pairs.The combined efficiency of these two kits in 2nd-degree kinship identification was 0.466 2.Conclusion The application value of MHSeqTyper47 kit is relatively higher in the identification of lst-degree kinships.If jointly used with the GlobalFilerrM kit,2nd-degree kinship identification could be achieved in some cases.

The geographical origin of forensic evidence provides important information for crime investigation and solving cases,and is one of the key elements of criminal cases.Previous studies have shown significant differences in the distribution of microorganisms in different regions.Detecting environmental DNA samples and inferring the geographical and spatial sources can provide clues and evidence for case handling.However,due to the diversity of criminal environments and the trace amount of frequently encountered exhibits,stable and reliable technical methods for inferring geographical origin from environmental DNA are not yet available.This article summarizes the sample collection and DNA extraction methods for four types of environmental samples:dust,soil,water,and air.It compares the differences between amplicon sequencing and metagenomic sequencing in studying environmental biological populations,outlines the full process of high-throughput sequencing-based data analysis,and focuses on reviewing the research progress in inferring geographical sources of environmental samples based on bacteria,fungi,and other eukaryotes,to provide references for establishing sequencing and analysis methods for environmental DNA in forensic DNA laboratories and exploring environmental DNA information for forensic applications.

Objective Sequencing depth is a key parameter in next generation sequencing,which is closely related to the accuracy of sequencing results.Forensic biological evidence examination requires extremely high accuracy.It is crucial to scientifically and reasonably set the sequencing depth analysis threshold for forensic next generation sequencing testing.Methods This study used targeted sequencing data of microhaplotypes from 50 samples with known genotypes.By calculating the accuracy,precision,recall,and F1 score of each locus under various threshold conditions,two types of analysis threshold setting methods,which were based on fixed read count and fixed sequencing depth ratio,were studied extensively.Results The results showed that false positives were observed when the analysis threshold was set at 50×or 100×.When the analysis threshold was set at 200×,false negatives were observed.When the analysis threshold was set at 1.5%,3.0%,or 4.5%,false positives were observed.This study further proposed a third type of analysis threshold setting method,which was based on sequencing depth ratio scatter plots.With this method,no false positive or false negative was observed in the results.This article then explored four factors that lead to significant differences in the sequencing depth of forensic next generation sequencing experiments,compared with the analysis threshold setting method for capillary electrophoresis technology,and discussed the correlation between analysis thresholds and the ability to distinguish mixed DNA.Conclusion Employing the sequencing depth ratio scatter plot method to set analysis threshold has significant application value in next generation sequencing-based forensic genetic marker genotyping.