For example, for breast cancer (MIM: 114480), GWASs have identified over 300 common susceptibility loci,1,2,3 while rare variants in ATM (MIM: 607585), BARD1 (MIM: 601593), BRCA1 (MIM: 113705), BRCA2 (MIM: 600185), CHEK2 (MIM: 604373), RAD51C (MIM: 602774), RAD51D (MIM: 602954), PALB2 (MIM: 610355), and TP53 (MIM: 191170) have been identified through linkage or targeted sequencing studies.4 The gene discussed is CHEK2; the disease is breast cancer.