Final answer:
p53 is phosphorylated in response to extensive DNA damage, which leads to cell cycle arrest and repair mechanisms. If the damage is irreparable, p53 initiates apoptosis. Mutations in p53 can prevent these processes, contributing to cancer development.
Step-by-step explanation:
The protein p53 plays a critical role in monitoring and responding to DNA damage within a cell. When DNA is extensively damaged, p53 is phosphorylated which essentially serves as a signal activation step. This activation of p53 leads to a halt in the cell cycle to allow time for DNA repair. If the DNA cannot be repaired, p53 then signals for apoptosis (programmed cell death), preventing the propagation of damaged genetic material.
Mutated forms of p53 found in over 50 percent of human tumor cells can lead to the inability of the cell to adequately detect and respond to DNA damage, therefore bypassing cell cycle arrest and repair, or apoptosis, and enabling the spread of cancerous cells.