Simplified low-copy-number DNA analysis by post-PCR purification.

Area of Science:

• Forensic Science
• Molecular Biology
• Genetics

Background:

• Standard forensic DNA profiling struggles with low-copy-number (LCN) samples due to insufficient DNA quantity.
• Increased amplification cycles are typically used for LCN samples, potentially introducing errors.

Purpose of the Study:

• To evaluate post-PCR purification methods for improving the sensitivity of DNA analysis.
• To determine the effect of purification on fluorescent allelic signal intensity in capillary electrophoresis.
• To establish a method for obtaining complete DNA profiles from minimal DNA templates.

Main Methods:

• A 28-cycle polymerase chain reaction (PCR) was employed.
• Purification techniques evaluated included filtration, silica gel membrane, and enzyme-mediated hydrolysis.
• The purified PCR products were analyzed for fluorescent allelic signal intensity using capillary electrophoresis.
• Comparison was made between purified and unpurified PCR products.

Main Results:

• A selected post-PCR purification method significantly increased the sensitivity of 28-cycle PCR.
• Full DNA profiles were consistently obtained from templates as low as 20 pg DNA.
• Genetic profiles were successfully obtained from mock case samples (fingerprints) using purification, while unpurified samples yielded no profiles.
• While allele dropout and stutter were observed, no contamination occurred in negative controls.

Conclusions:

• Post-PCR purification is an effective strategy to enhance DNA profile generation from LCN templates.
• This method increases the sensitivity of capillary electrophoresis, allowing DNA profiling from <100 pg DNA with standard 28-cycle amplification.
• The described purification method improves the reliability of forensic DNA analysis on challenging samples.