Diatom DNA Barcodes And Forensic Applications Of Micro Haplotypes

Diagnosing of drowning,inferring drowning site and individual identification are important aspects of forensic expertise,and also challenging problems in forensic science.Drowning is a common cause of accidental death.The location of bodies found in water is always not the actual drowning site.Therefore,inferring the drowning site is important for identifying the corpse source.In forensic ancestry inference,finding efficient ancestry inference genetic markers to predict regional information of unknown Individuals can reduce the scope of investigation and provide clues for solving cases.Hence,the study set up the winter and autumn diatom DNA barcode database for inferring the drowning site and search high efficient ancestry inference microhaplotypes for ancestry inference.Diatom is a widely distributed single cell microorganism which is stable and can resist extreme environment.Diatom examination is an important way in inferring drowning site and postmortem water interval.In this study,we divided Nanjing section of the Yangtze River into 10 sampling points according to longitude and latitude.Winter water samples were collected from each sampling point during December 2016 to January 2017 and autumn samples were in September 2018.Our study set up the Yangtze River’s winter and autumn diatom morphological distribution database,and further developed DNA barcode data.Autumn and winter diatom research supported that sampling location and season were two main factors for diatom distribution.Therefore,it is necessary to establish a multi-site and long-term diatom detection strategy for further analysis.On the basis of molecular biology technology,DNA barcode could enrich the diatom polymorphism and showed potential application opportunity in forensic science.To handling the large data which would waste time and energy for manual work in electron analysis,our study proved that the potential of machine learning in auto-recognizing the diatom picture.The use of DNA to determine the ancestry of an individual is becoming more and more important in the areas of forensics.Kidd et al have been the first to identify and catalog haplotypes,termed as microhaplotypes(≤200 bp),with potential use in forensic biogeography analysis.In the present study,we selected 35 short ancestry informative microhaplotypes by calculating the informativeness(I_n)according to Rosenberg et al.In total,2504 individuals from 26 populations and 5 areas in 1000Genomes Project database as reference data to search the loci and 279 individuals from 147 populations and 7 areas were used to test the ancestry inference power of selected ancestry inference microhaplotypes.STRUCTURE,principal coordinate analysis,the well-known neighbor joining algorithm and machine learning technology were performed to analysis the data.The results of population structure analysis demonstrated that populations from 1000G or SGDP can be accurately separated and clustered.The predicting accuracy rate of unknown individuals to populations or continents they belong to is relatively high.Overall,the results suggested that microhaplotypes could be a valid complementary tool in forensic ancestry inference and had potential in drowning corpse’s individual identification.