Illustrations of PCR amplification and size of fragments. The common primers (A) flank and amplify the non-specific-allele amplicons while the allele-specific primers (B) amplify the specific-allele amplicons to allow the differentiation of the genotypes. The DNA sequences were retrieved from GenBank (National Center for Biotechnology) using accession numbers (C). The non-specific-allele amplicons act as internal positive control (E). dsDNA = double-stranded DNA, Wt = wild-type, Vt = variant-type.