The segments of the genes that contain the nucleotide variations (single nucleotide polymorphisms) of interest are amplified by PCR. PCR
products are subjected to a multiplex primer extension reaction (PEXT) using allele-specific primers. Only the primer whose 3 end is fully
complementary to the target is extended by the DNA polymerase. Biotin (circled B) is incorporated in the extended fragment. The extension
product is directly applied to the dipstick-type biosensor.