Systems and methods for diagnosing or characterizing a predisposition to colon cancer are provided. Cell nuclei may be evaluated for the presence or quantity of gamma-H2AX foci. Nucleic acids may be evaluated for the presence, type, or quantity of genomic instability or surrogates of dsDNA breaks such as ataxia telangiectasia mutated (ATM), Rad3-related protein (ATR), and Tumor suppressor p53-binding protein 1 (53BP1) in gamma-H2AX foci. Nucleic acids comprising a germline nucleic acid sequence of the ERCC6, WRN, TERT, and FAAP100 genes may be sequenced or probed to determine if the nucleic acid sequence includes one or more alterations that cause genomic instability, dsDNA breaks, or gamma-H2AX foci or otherwise predispose a subject to develop colon cancer.