38 Insertion-deletion (InDel) markers analysis and its application in forensic cases

The typing of short tandem repeats (STRs) is a common method used in forensic laboratories based on its good performance. However, because of the relatively large size of amplicons (150–500 bp), most of them are unsuitable for degraded DNA and low copy number samples. So, there is a need to find new genetic makers with smaller amplicon size. Recently, some forensic researchers focused their attention to alternative and supplementary genetic markers in the human genome: insertion-deletion polymorphisms (InDels). They are diallelic, of smaller size, widely distributed throughout the genome and with a lower mutation rate compared to STRs. Due to their characteristics, InDels can aid forensic analysis even when a very small amount of DNA is available in a sample. In this study we tested the ability of a set of 38 InDel markers on genotyping different forensic samples containing low DNA concentration, already typed using the Identifiler kit but obtaining poor results. Statistical analysis was performed using the STRs results with appropriated softwares. After, InDel typing results were added to the STRs statistic calculations. The purpose of this work was to verify the actual usefulness of InDels analysis in order to improve the weight of the statistical analysis of challenging samples.