Location of KRAS codon 12 and 13 mutations and PCR amplicons. Exon 2 of KRAS is shown from the ATG without the untranslated region. The position and size of the PCR amplicons used in the HRM assays in relation to exon 2 of KRAS is indicated. There are 12 possible single base mutations that can occur at codons 12 and 13 of KRAS. All possible mutations are listed along with the corresponding amino acid changes. These mutations are located at positions 64, 65, 67 and 68 of the 189 bp PCR amplicon and at positions 53, 54, 56 and 57 of the 92 bp PCR amplicon.