For instance, Mre11, Nbs1, ATM and BRCA1, which play critical roles in DNA damage checkpoint and DSB repair are linked ataxia-telangiectasia-like disorder (ATLD), Nijmegen breakage syndrome (NBS), ataxia-telangiectasia and familial breast cancer, respectively [5]–[9]. The gene discussed is ATM; the disease is ataxia-telangiectasia-like disorder.