Digital single-nucleotide polymorphism analysis for allelic imbalance

Digital single-nucleotide polymorphism (SNP) analysis is developed to amplify a single template from a pool of DNA samples, thereby generating the amplicons that are homogeneous in sequence. Different fluorophores are then applied as probes to detect and discriminate different alleles (paternal vs maternal alleles or wild-type vs mutant), which can be readily counted. In this way, digital SNP analysis transforms the exponential and analog signals from conventional polymerase chain reaction (PCR) to linear and digital ones. Digital SNP analysis has the following advantages. First, statistical analysis of the PCR products becomes available as the alleles can be directly counted. Second, this technology is designed to generate PCR products of the same size; therefore, DNA degradation would not be a problem as it commonly occurs when microsatellite markers are used to assess allelic status in clinical samples. Last, digital SNP analysis is designed to amplify a relatively small amount of DNA samples, which is available in some clinical samples. Digital SNP analysis has been applied in quantification of mutant alleles and detection of allelic imbalance in clinical specimens and it represents another example of the power of PCR and provides unprecedented opportunities for molecular genetic analysis.