An innovative transfer DNA experimental design and qPCR assay: Protocol and pilot study

Area of Science:

• Forensic Science
• Genetics
• Molecular Biology

Background:

• Forensic "touch" DNA samples are often low-quantity and can originate from multiple individuals.
• Distinguishing between primary and secondary DNA transfer is challenging.
• Understanding DNA transfer mechanisms is crucial for accurate forensic investigations.

Purpose of the Study:

• To develop an innovative protocol for differentiating primary and secondary DNA transfer.
• To evaluate a cost-effective quantitative PCR (qPCR) assay for detecting low concentrations of male and female DNA in mixed samples.
• To establish rates of primary and secondary DNA transfer in realistic forensic scenarios.

Main Methods:

• A paired male and female DNA transfer experimental design was employed.
• A quantitative PCR (qPCR) assay targeting a sex-specific region of the Amelogenin gene was utilized.
• Experimental DNA samples were tested using the developed transfer DNA protocol.

Main Results:

• The Amelogenin qPCR assay successfully detected low concentrations of male and female DNA in mixed samples.
• Male DNA was detected in most mixed samples, even when outnumbered 4:1 by female DNA.
• Primary DNA transfer was identified in 100% of trials, and secondary transfer in 37.5% of trials.

Conclusions:

• The developed protocol effectively differentiates primary and secondary DNA transfer.
• The cost-effective qPCR assay is capable of detecting low-level DNA mixtures.
• This innovative method provides a simplified approach to establishing DNA transfer rates in forensic casework.