Challenging to p53 importance in normal cellular homeostasis was the observation that that p53-null mice developed no overt defects and were viable, suggesting that p53 was dispensable for normal embryonic development [13,64], albeit a higher percentage of female mice were infertile, and mice were found to be more vulnerable to carcinogens, with increased overall cancer risk [13,64]. The gene discussed is TP53; the disease is cancer.