Applying a PCR inhibitor tolerant DNA polymerase blend in forensic DNA profiling

Crime scene samples often contain extraneous compounds that may interfere with PCR-based DNA analysis, resulting in imbalanced, partial or blank/negative DNA profiles. Customising the chemical content of the PCR reaction is a strategy that may increase PCR inhibitor tolerance without manipulating the sample. We have validated a modified version of AmpFlSTR SGM Plus, replacing AmpliTaq Gold DNA polymerase with a customised blend of two alternative polymerases, ExTaq Hot Start and PicoMaxx High Fidelity. Allele calls are identical to standard analysis. Stutter sizes and balance values are indistinguishable. The modified chemistry provides increased resistance to PCR inhibitors, resulting in an elevated number of detected alleles for various problematic crime scene samples.