Promega Engineers New Enzyme To Significantly Reduce Stutter in Forensic DNA Analysis

A novel enzyme developed by research scientists at Promega Corporation will virtually eliminate confounding stutter artifacts in forensic DNA analysis. The reduced stutter polymerase dramatically simplifies mixed sample deconvolution and allows forensic analysts to generate accurate profiles of multiple contributors. This is the first enzyme to solve one of the biggest challenges in DNA forensics.
 
“By eliminating stutter artifacts, an analyst can more accurately identify low-level contributors and better determine the number of contributors in highly complex mixtures.” says Michael Coble, Executive Director of the Center for Human Identification at the University of North Texas Health Science Center.

Stutter has been a major pain point for the forensics community for decades. The naturally occurring errors may cause analysts and software to discard potentially useful pieces of data. Using the new polymerase developed by Promega, analysts will no longer have to sort through small peaks to separate useful data from noise.

“Because they don’t have to worry about stutter peaks anymore, forensic DNA analysts will be able to get more valuable information out of each sample,” says Bob McLaren, Director of Research at Promega. “Hopefully, that will lead to solving more cases, and doing it all much faster.”

This innovation was first announced at the International Symposium on Human Identification. Promega has applied for a patent covering this novel enzyme for use in STR analysis.

Stutter in STR Analysis

Forensic DNA analysis is based on the amplification and detection of short tandem repeats (STRs). STRs are regions of DNA where short sequences are repeated multiple times in a row. When the sequence is being amplified using Taq polymerase, the enzyme has an occasional tendency to slip across the repeats, resulting in a new fragment that is one repeat shorter than the template. When the fragments are separated and detected by capillary electrophoresis, the data will show an extra peak that is one repeat shorter than the true peak.

This creates challenges when a sample contains DNA from multiple contributors. It can be extremely challenging to determine whether a peak represents stutter or an allele from a minor contributor. This is a longstanding pain point for forensic DNA analysts.

Reduced Stutter Polymerase

The novel enzyme announced by Promega is a genetically modified version of Taq polymerase that includes features from T7 DNA Polymerase and additional mutations that allow it to more tightly bind to its template strand. The result is an enzyme that reduces stutter by an order of magnitude relative to current systems, rendering it undetectable behind instrument baseline noise.

Promega plans to integrate the new reduced stutter polymerase into future 8-colour STR analysis kits. Promega is also the first manufacturer to launch 8-colour STR chemistry, which enables analysts to generate more data from complex or degraded samples. When analysed on the Spectrum CE System, the combined technologies will empower forensic laboratories to generate the most reliable and high-quality data for forensic casework.

Promega has been developing and manufacturing products for DNA-based human identification for more than 35 years.