Typical examples are HBOC (BRCA121/222) and its related cancer susceptibilities designated as ‘HR-deficiency (HRD)’(RAD5034, RAD5135, RAD51C36,37/D38, BARD139, BRIP140, PALB241), Nijmegen breakage syndrome (NBS142) and LIG4 syndrome (LIG443). The gene discussed is LIG4; the disease is cancer.