Heteroduplex Analysis is a Rapid Method for the Detection of Suballeles Caused by Mixed Length and Sequence Variability in Short Tandem Repeat Systems

Abstract

STR polymorphisms differ in the number of the tandem repeats. However, in addition, a microheterogenity, as far as the sequence variation is concerned, has been detected in some systems (HumVWA and others) (Möller 1994). The aim of our paper is to demonstrate the usefulness of the heteroduplex (HD) analysis (HDA) for the detection of suballeles in DNA systems such as HumVWA (Kimpton 1992), HumCD4 (Edwards 1991) and Hum Dysl9 (Roewer 1992). The HDA is a well-established technique (Wilkin 1993) but, to our knowledge, HDA is not usual in forensic application. During PCR amplification, the DNA products are submitted to a melting and a reassociation process. In case of a homozygous genotype, the reassociation produces only homoduplexes. However, if there are DNA fragments with different numbers of repeats and/or significant differences concerning the sequence, the reciprocal association produces two or more types of HDs in addition to homoduplexes. On dependency on the extension of the missmatch area, the HDs migrate noticeably slower than homoduplexes in the nativePAGE. Thus, HD can provide several pieces of information which remain hidden, if only measurements of the length are performed.