Development of an Alu-based, real-time 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. We have previously described a method for quantitation of human DNA based on PCR amplification of a repetitive Alu sequence that uses a fluorescence plate reader. This manuscript describes and validates a variation of this assay using real-time PCR and SYBR Green I for quantitation. The advantages of the real-time assay over the plate reader assay are: reduced hands-on time, lower assay cost, and a greater dynamic range. The main disadvantage is the cost of the real-time instrument. However, for those forensic laboratories with access to a real-time instrument, this Alu-based assay has a dynamic range of 16 ng to 1 pg, is sensitive, specific, fast, quantitative, and uses only 2 microL of sample.