Development of an Alu-based,QSY 7-labeled primer PCR method for quantitation of human DNA in forensic samples

Determining the amount of human DNA extracted from a crime scene sample is an important step in DNA profiling. The forensic community relies almost entirely upon a technique (slot blot) to quantitate human DNA that is imprecise, time consuming, and labor intensive. This paper describes the development of a new technique based on PCR amplification of a repetitive Alu sequence. Specific primers were used to amplify a 124-bp fragment of Alu sequence; amplification was detected by SYBR Green I staining in a fluorescent plate reader. To reduce background in the plate reader assay, QSY-7 labeled primers were utilized. The assay was tested on animal DNAs, human blood spots, mock crime samples, and degraded DNA in comparison with the slot blot technique. The QSY Alu assay has a dynamic range of 10 ng to 10 pg, and is sensitive, specific, fast, quantitative, and comparable in cost to the slot blot assay.