Research On X-InDel Polymorphisms For Forensic Application

Objective Screening InDel loci to form a forensic DNA genetic marker database for Chinses population through the molecular biology research and population genetic investigation of Insertion/Deletion polymorphism (InDel) on the X chromosome. On this basis, a typing system auxiliary is built as the supplymentary tool for forensic application in the Chinese population.Methods Several candidate InDel markers on the X chromosome were selected to form a InDel database for forensic DNA testing using the Human Genome Browser in Galaxy system and dbSNP database. Multiplex PCR primer pairs of selected X-InDel markers were designed using Primer Premier 5.0 software, labeled by FAM, HEX and TAMRA fluorescence dye. Genetic polymorphisms of 5 main ethinic groups of China, including Han nationality were investigated with the developed multiplex PCR system.Results A database of the InDel markers on the X chromosome was built to supply necessary information for forensicn use. Additionally, a new multiplex genotyping system, named InDel X-18PLEX, was successfully developed and validated in this study. The InDel X-18PLEX system consisted of 18 InDel markers on the X chromosom and 1 Amelogenin gender marker. No deviation from HWE expectations was detected in the distribution of female genotypes in the 5 investigated ethnic groups. However, there is significant difference between their distributions. From the investigation of Han nationality, high female (0.9999994) and male (0.99988) overall discrimination power values were obtained, as well as high overall mean exclusion chance values in father/mother/daughter trios (0.999992) and in father/daughter duos (0.99).Conclusion InDel X-18PLEX meets the requirements as a forensic DNA complementary kit, providing effective supplementary analysis tools for difficult cases in forensic paternity and identification.