Matching vs. mismatching nucleotide is placed at the 3'-end of the primer for best discrimination results.
Cilantro: some people love it in their food, some hate it. Here we are detecting a genomic SNP (rs72921001) in HeLa genomic DNA. This SNP is reported to be close to a number of genes coding for olfactory receptors. (Reference: Eriksson N. et al. (2012), "A genetic variant near olfactory receptor genes influences cilantro preference.")
Considering, that only the C-allele specific primer is extended and yielding in a specific amplicon, we can conclude a genetic predisposition in disliking cilantro, as this SNP is significantly associated with detecting a soapy taste to cilantro.
Allele-specific PCRs were performed from 1 ng/µl of HeLa gDNA in the presence of a realtime dye, indicating the amplification of the C-allele specific primer only. The A-allele specific primer is discriminated, thus not amplified up to 50 cycles.
PCR products were subsequently analysed on a 2.5% agarose gel. Specific product is visualized by ethidium bromide staining at the amplicon length of 109 bp.