In the F1 heterozygous mule, genes with mutations in DNA sequences were also highly concentrated in DNA replication (e.g., PRIM1, POLD2), DNA repair (e.g., PMS2 and MSH2), and cancer, such as proto-oncogenes (e.g., KRAS, HRAS) and tumor-suppressor genes (e.g., APC, PTEN). This evidence concerns the gene POLD2 and cancer.