 These high-throughput platforms have not progressed beyond the proof-of-principle stage and so far the Invader system has not been used in any large scale SNP genotyping projects.Primer extension is a two step process that first involves the hybridization of a probe to the bases immediately upstream of the SNP nucleotide followed by a ‘mini-sequencing’ reaction, in which DNA polymerase extends the hybridized primer by adding a base that is complementary to the SNP nucleotide.This incorporated base is detected and determines the SNP allele (Goelet et al.