ATR and Nijmegen breakage syndrome: For example, mutations of ATM lead to Ataxia-Telangiectasia (A-T), of ATR lead to Seckel Syndrome (ATR-SS), of components of the MRN complex cause Ataxia-Telangiectasia-like disorder (A-TLD, mutations in MRE11), Nijmegen breakage syndrome-like disorder (NBSLD, mutations in RAD50) and Nijmegen breakage syndrome (NBS, mutations in NBS1), respectively.