Combining allele-specific fluorescent probes and restriction assay in real-time PCR to achieve SNP scoring beyond allele ratios of 1:1000.

TaqMan-nuclease assays are widely used for the qualitative detection of single nucleotide polymorphisms (SNPs) and the determination of biallelic states in pooled or heterozygous DNA samples. These assays are highly specific, reproducible, and suitable for high-throughput approaches. A crucial limitation of this method, and others, is the detection qf minor allele frequencies with detection limits of generally 3% to 9% for minor allele contributions. Here we describe the combination of customized TaqMan-nuclease assay and allele-specific restriction to increase the sensitivity of this method, allowing the qualitative detection of allele contributions as low as 0.05%.