The newly disentangled patterns of mutations were termed mutational signatures. Instead of clustering cells by mutational composition, PyClone clusters mutations that have similar cellular frequencies. Epigenetic alterations are much more frequent in colon cancer than genetic (mutational) alterations. Developmental or mutational biases have also been observed in morphological evolution. All mutagens have characteristic mutational signatures with some chemicals becoming mutagenic through cellular processes. In cancer, a number of mutational changes are found in protein coding genes. By itself, RecG was found to not necessarily lead to a mutational phenotype. Instead, a network of genotypes are connected via mutational paths. Both mutational and selective pressure can independently introduce asymmetry in DNA strands. Additionally, DNA repair mechanisms can introduce mutational errors when repairing physical damage to the molecule. Deep mutational scanning has also been used to infer protein-protein interactions. Deep mutational structure can also be used to infer protein structure. This was discovered by doing mutational analyses. However, sudden morbidity and mortality can occur regardless of mutational status. KRAS mutational analysis is commercially available from a number of laboratories.