Forensic Use of Short Tandem Repeats via PCR

Abstract

The DNA sequence of man’s chromosomes has the potential for wide variation from individual to individual since only 1% encodes functional elements, i.e. genes. Sequence differences were first detected by restriction fragment length polymorphisms (RFLPs) using the Southern method (Southern, 1975). These two-allele polymorphisms were used for mapping Huntington disease locus and diagnosis of both B-thalassemia and sickle cell disease. Jeffreys (1985b) and Nakamura (1987) subsequently described a new class of RFLPs which arise from repeated sequences occurring in different copy numbers from individual to individual. They were referred to as satellite sequences or variable number of tandem repeats (VNTR). These highly informative repeat sequence polymorphisms have been used extensively in the mapping of human disease genes such as cystic fibrosis (CF) and neurofibromatosis (NF), and more relevant to this meeting, for personal identification (Jeffreys et al. 1985a) (Gill et al. 1985). The method of identification was Southern analysis. At many of these loci, the repeat sequences are smaller than the resolving power of agarose gels, so discrete alleles will not be differentiated. Despite this shortcoming, the large number of alleles provides a very powerful DNA-based personal identification method.