STR DNA typing: increased sensitivity and efficient sample consumption using reduced PCR reaction volumes.

Area of Science:

• Forensic Science
• Molecular Biology
• Genetics

Background:

• Forensic DNA typing relies on Polymerase Chain Reaction (PCR) for DNA amplification.
• Reducing PCR reaction volumes offers potential benefits like improved sensitivity and reduced sample consumption for crime scene DNA.
• Optimizing PCR conditions is vital for analyzing limited and precious forensic samples.

Purpose of the Study:

• To investigate the impact of reduced PCR reaction volumes on DNA profile quality and sensitivity in forensic DNA typing.
• To determine the optimal template DNA concentration and PCR volume for reliable amplification of forensic samples.
• To assess the effect of decreased reaction volumes on signal intensity and heterozygous balance in forensic casework.

Main Methods:

• Utilized a nine-loci megaplex for amplification of experimental DNA mixtures.
• Tested 15 different template DNA to PCR reaction volume ratios using adjudicated casework samples.
• Analyzed amplification products for stoichiometric amplification, accurate detection, signal intensity, and heterozygous peak height ratio (HR).

Main Results:

• Stoichiometric amplification and accurate detection were achieved with experimental mixtures.
• Reducing PCR reaction volume to 10 microL and DNA to 0.500 ng yielded identical profiles with consistent signal intensity and HR.
• Further reduction to 5 microL and 0.063 ng slightly affected HR in one to three short tandem repeat (STR) loci.

Conclusions:

• Reduced PCR reaction volumes can enhance detection limits and sensitivity in forensic DNA typing.
• Optimized reduction in PCR volume and template DNA conserves irreplaceable crime scene samples.
• This approach improves the efficiency and effectiveness of forensic DNA analysis from limited samples.