Although the classification of tumor suppressor genes into these categories is helpful to the scientific community, the potential role of many genes cannot be reliably identified as the functions of many genes are rather ill-defined.  In some contexts, genes exhibit discrete caretaker function while in other situations gatekeeper characteristics are recognized.  An example of one such gene is p53.  Patients with Li-Fraumeni syndrome, for example, have mutations in the p53 gene that suggest caretaker function.  p53 has an identified role, however, in regulating the cell cycle as well, which is an essential gatekeeper function.