8. The effect of the deletion of one copy of the gene encoding p53 is different from the effects caused by other p53 mutations. For example, some loss-of-function mutations in the DNA-binding domain of p53 cripple its function as a transcription regulator. Such a mutation in only one copy of the p53 gene can be enough to confer a p53 loss-of-function phenotype, even when the other copy of the gene on the homologous chromosome is wild type. This is because ... (A) p53 is a proto-oncogene. (B) these mutations are recessive. (C) p53 is a tumor suppressor. (D) p53 forms a tetramer.