In skin cancer, the incidence of p53 mutations ranges from 50 to 90% in humans and mice.17, 18 Mutant p53 provides keratinocytes an advantage over normal keratinocytes in response to successive UVB exposure by evading cell cycle checkpoints and by allowing mutant keratinocytes to evade UVB-induced apoptosis.17, 19, 20, 21, 22, 23, 40 These events promote genomic instability, clonal expansion and the development of skin cancer. The gene discussed is TP53; the disease is skin cancer.