Applications of PCR to the Analysis of Biological Evidence

The ability to detect DNA polymorphisms in biological evidence samples has revolutionized forensic biology. Using restriction fragment length polymorphism (RFLP) analysis, individual-specific DNA “fingerprints” can be obtained, provided that the DNA is relatively undegraded and present in sufficient quantity. At least 50 ng of high molecular weight DNA is required for RFLP analysis using a single locus probe1 and greater than 100 ng for multilocus probe analysis.2 However, these amounts of undegraded DNA are frequently not available from forensic evidence in practice. For this reason, some forensic cases involving biological evidence are not amenable to RFLP analysis. Moreover, RFLP consumes a large amount of material and so many samples cannot be re-analyzed.