Chapter 3 - Historical Methods

Abstract

The human identity testing community has used a variety of techniques including single-locus probe and multi-locus probe restriction fragment length polymorphism (RFLP) methods and more recently polymerase chain reaction (PCR) based assays. Numerous advances have been made in the past quarter of a century in terms of sample processing speed and sensitivity. Instead of requiring large bloodstains with well-preserved DNA, tiny amounts of sample—as little as a few cells in some forensic cases—can yield a useful DNA profile. The gamut of DNA typing technologies used during the past several decades for human identity testing is compared in this chapter. The various DNA markers have been divided into four quadrants, viz., pre-DNA years (1900–1985); first decade of DNA testing (1985–1995); early PCR-based DNA testing; and second decade of DNA testing (1995–2005), based on their power of discrimination, that is, their ability to discern the difference among individuals, and the speed at which they can be analyzed. New and improved methods have developed over the years such that tests with a high degree of discrimination can now be performed in a few hours. The methods discussed in the chapter are blood group typing; protein profiling; RFLP with single-locus variable number of tandem repeat probes; DQA1 PM; D1S80; silver-stained short tandem repeats (STRs); fluorescent STRs; and mitochondrial DNA sequencing.