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Improved Detection of Male DNA in Post-Coital Samples

NCJ Number
Date Published
June 2012
106 pages
This is the final report on a project that developed a method of overcoming problems associated with the detection and analysis of low levels of male DNA in a background of female DNA, which often occurs in sexual assault cases.
The method developed involves a selective amplification of loci in Y-chromosomal genomic DNA prior to Y-STR analysis. This genomic partitioning is effective in further increasing the signal to noise ratio of the Y-chromosomal DNA compared with the female epithelial DNA, thus enabling clear male profiles to be obtained. The use of the nested PCR pre-amplification prior to Y-STR analysis allows the recovery of Y-STR profiles from as little as 5 pg of male DNA from various body fluids and tissues (blood, semen, saliva, and skin). No interference from female DNA was observed even with female DNA in 100,000-fold excess of male DNA. Male DNA was analyzed in post-coital samples obtained approximately 5 days after intercourse. In addition, such an approach could be used to improve the analysis of touch or contact DNA samples, which often contain small amounts of male DNA. The researchers developed a 17-locus Y- chromosome specific nested PCR pre-amplification multiplex. Initial validation studies have been conducted in order to show this method's usefulness with forensic samples. Extensive tables and figures, 47 references, and a listing of publications and presentations of study findings

Date Published: June 1, 2012