In this context, the behavior of p53-mutant cells may be considered paradigmatic: some cancers retain their p53 mutation after treatment; other cancers harbor multiple single nucleotide variation or copy number alterations that can be lost, gained or change in their frequency after treatment; finally, in other cancers, p53 mutations can be lost in the absence of CNAs, since the mutant p53 resides in tumor cell clones that are lost as they pass through a genetic bottleneck [14]. The gene discussed is TP53; the disease is cancer.