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Genetic Bit Analysis (GBAÔ) is a solid phase system designed to type single nucleotide polymorphisms (SNPs) GBAÔ consists of two procedural components; sample processing and product detection. Processing includes a simple DNA isolation, PCR amplification of loci containing target SNPs, and the 5'-3' elimination of one strand of the PCR product using exonuclease. Detection involves the hybridization of the remaining single-stranded product to an immobilized indicator primer, extension of the indicator primer by a labeled chain terminator, and detection of the extended product by enzyme-linked colorimetry. This paper examines the application of GBAÔ to the typing of forensic loci traditionally assayed using SSO reverse-dot blot based systems.

Two hundred human DNA sample extracts, previously typed using the Perkin-Elmer Amplitype PMÔ kit, were retyped at genetic loci D7S8, LDLR and GYPA using the GBAÔ method. Comparisons of typing results revealed a high degree of fidelity between the two systems. Samples that gave discordant results were further characterized by DNA sequencing. Comparison data between systems, and sequencing data characterizing discordant samples will be presented.

There are several features that make GBAÔ an appealing DNA typing system. Since any SNP has the potential to be typed using GBAÔ, there is greater flexibility in test configuration. The detection chemistry provides a "pass no pass" result, removing subjective interpretation. The 96-well plate format of GBAÔ is adaptable to automation allowing time savings in all areas of testing, from sample processing to final data analysis. Finally, the high sample throughput allowed by automation means that the cost per-locus tested is comparatively low.