Promega Paradyme 27GY STR System

Promega Corporation has launched the Paradyme 27GY STR System, a short tandem repeat (STR) analysis kit featuring the company’s Reduced-Stutter Polymerase (RSP). This novel enzyme, engineered by Promega, reduces the most common type of confounding artefact in forensic DNA analysis.

Stutter has been a major challenge of forensic DNA analysis for decades. When DNA is amplified using Taq polymerase, the enzyme occasionally slips across repeated sequences, resulting in a new fragment that is shorter than the original. When the sample is analysed by capillary electrophoresis, the resulting electropherogram will show an extra peak that is one repeat shorter, and sometimes one repeat longer, than the true peak. These extra peaks create challenges for analysis when a sample potentially contains DNA from multiple contributors. It is difficult to determine whether a peak represents stutter or an allele from a minor contributor.

The enzyme included in the kit is engineered to minimise the ‘slippage’ during amplification of repetitive DNA sequences common in forensic DNA analysis. It is said to reduce stutter signal intensity by an average of eightfold relative to current systems, often rendering it undetectable from instrument baseline noise. This minimises a significant source of uncertainty in forensic casework. As a result, labs should be able to provide conclusive results for complex mixtures, generate more accurate profiles for casework and databases, and decrease their turnaround time for sample analysis.

The kit is an eight-dye multiplex that includes 23 autosomal STR loci, Amelogenin and key Y-STR loci, supporting CODIS core loci requirements and the expanded CODIS framework used by crime laboratories in the United States and internationally. Compared to current systems, its benefits are said to include: fewer data edits, reducing time spent on analysis; reduced stutter and Y-STR loci, improving number-of-contributors (NoC) determination accuracy; high interpretation confidence with complex mixtures, reducing analyst fatigue and secondary technical review effort; increased minor contributor detection in mixtures; more loci amplified from degraded samples using shortened-amplicon eight-dye multiplex; and Quality Indicator peaks that support an informed assessment of amplification success and sample quality troubleshooting.