BRCA1 and cancer: The fact that most cancer genes show a high degree of conservation between human and chimpanzee, prompted us to analyze in more detail the observed changes in genes previously reported to be of special relevance in human cancer, such as the tumor suppressors p53 and BRCA1. We found that chimpanzee p53 shows a single amino acid difference with human p53, resulting in a protein containing Pro instead of Arg at position 72.