Development of a real-time method to detect DNA degradation in forensic samples

Area of Science:

• Forensic Science
• Molecular Biology
• Genetics

Background:

• Assessing DNA degradation is crucial for selecting appropriate forensic analysis methods, such as standard short tandem repeats (STRs), mini STRs, or mitochondrial DNA (mtDNA).
• Current methods may not adequately predict the extent of DNA damage in compromised samples.

Purpose of the Study:

• To develop and optimize a sensitive real-time PCR assay for detecting DNA degradation.
• To establish a reliable method for predicting DNA sample quality based on amplicon ratios.

Main Methods:

• Developed a Plexor® technology/real-time PCR assay utilizing a common forward primer and two distinct reverse primers to amplify two Alu fragments (63 bp and 246 bp).
• Optimized assay parameters including reaction volume, cycle number, and thermal conditions.
• Validated the assay using DNaseI-treated DNA, environmentally degraded samples, and samples with common forensic inhibitors.

Main Results:

• The ratio of short to long amplicon concentrations (degradation ratio) increased with DNA degradation time.
• The degradation ratio effectively predicted the loss of larger STR loci in compromised forensic samples.
• The assay demonstrated high sensitivity and robustness against various degradation factors and inhibitors.

Conclusions:

• The developed real-time PCR assay provides a sensitive and reliable method for assessing DNA degradation in forensic samples.
• This assay can guide the selection of optimal DNA analysis techniques, improving the success rate of forensic investigations.
• The degradation ratio serves as a valuable predictive marker for DNA sample quality.