Genes with low penetrance such as androgen receptor (AR), checkpoint kinase 2 (CHEK2), E-cadherin, Nijmegen breakage syndrome 1 (NBS1), RAD50, BRCA1 interacting protein C-terminal helicase 1 (BRIP1), and partner and localizer of BRCA2 (PALB2) are frequently mutated in the general population and play an important roles in the occurrence of breast cancer (11). The gene discussed is CHEK2; the disease is breast cancer.