Re-evaluation of the Current NMI01 STR Sizing System of Cannabis DNA
The NMI01 STR region of Cannabis sativa DNA is currently developed for source attribution of seized Cannabis by law enforcement. However, the current system does contain some limitations, mainly the lack of a commercially available allelic ladder in conjunction with the GeneScan 500 internal size standard. As part of an extended study on the stability of plant DNA on evidence collection cards, FTA cards with seized Cannabis from 2009 and 2012 and fresh samples were amplified using CS1F and CS1R primers. Overall, the alleles 2, 16.1, 22.1, 23, 26, 28, and 30.1 were chosen to include in the proposed custom NMI01 allelic ladder. The sizing program Open Source Independent Review and Interpretation System (OSIRIS) was modified for the NMI01 bin sets as it contains its own custom-sizing algorithm using double Gaussian sizing compared to the Local Southern method used in GeneMapper. Although OSIRIS with an allelic ladder and the current system with GeneMapper exhibited similar sizing precision, the sizing software OSIRIS was a significant improvement over the current system with GeneMapper when comparing allele call accuracy. Overall, this research study has shown that modifying the NMI01 system for the automated sizing software OSIRIS along with the use of a further comprehensive allelic ladder may help the current system approach 100% accuracy in correct allele assignment.