Microsphere-Based Single Nucleotide Polymorphism Genotyping

Single nucleotide polymorphisms (SNPs) are single base differences in genomic DNA (1 ). These single-base mutations, estimated to occur every 1000 bases, are thought to represent the most common form of genetic variation in the human genome (2 ). Several million SNPs have been identified (3 ). High-throughput analysis of these variations will be required to understand their contribution to disease. We outline a method that uses solution-based oligonucleotide ligation assay (OLA) (4 ) or singlebase chain extension (SBCE) (5 ,6 ) for allele discrimination followed by hybridization to fluorescently encoded microspheres. Flow cytometric analysis of the microspheres’ fluorescent profile yields rapid and accurate SNP genotyping (7 ,8 ).