In colorectal cancer, most KRAS mutations are in the codons 12 (about 80%) and 13 (about 15%) of exon 2 and in the codon 146 of exon 4 (about 4%); the remaining are in the codons 59-61 of exon 3 and in the codon 117 of exon 4 (45). This evidence concerns the gene KRAS and colorectal cancer.