What role does p53 normally play in healthy cells?

The role of p53 in healthy cells is primarily to induce apoptosis in response to cellular stress, such as DNA damage. p53 is known as the "guardian of the genome" because it plays a critical role in maintaining genomic stability. When DNA damage occurs, p53 is activated and can halt the cell cycle to allow for repair mechanisms to correct the damage. If the damage is too severe and cannot be repaired, p53 triggers programmed cell death, or apoptosis, to prevent the propagation of potentially cancerous cells.

This function is vital for preventing the development of tumors, as the loss of p53 activity is often associated with cancer progression. In contrast, promoting rapid cell division (which would potentially lead to cancer), inhibiting all forms of cell growth indiscriminately, or enhancing differentiation does not align with p53's established role in cellular health and tumor suppression. Thus, the correct answer captures the essential protective mechanism of p53 in preserving cellular integrity and preventing cancerous transformations through apoptosis.