Final answer:
In response to DNA damage, activation of p53 is responsible for arresting the cell cycle to allow for repair, or initiating apoptosis if repair is unachievable, thereby preventing the passage of defects to daughter cells. Option number a is correct.
Step-by-step explanation:
A key aspect of cellular self-maintenance is the ability to repair DNA damage and resume the cell cycle, which is a critical process often overseen by the p53 protein. If cellular damage is detected, p53 rapidly halts the cell cycle and activates mechanisms to repair the DNA.
If the DNA can be repaired, p53 allows the cell cycle to proceed; however, if the damage is irreparable, p53 initiates apoptosis to prevent the proliferation of damaged cells. The transition to allow the cell cycle to resume after successful repair or to proceed to apoptosis when repair is impossible is promoted by the activation of p53, which induces other responses such as cell cycle arrest or DNA repair, demonstrating its role as a tumor suppressor. Therefore, the correct answer to the student's question is A) Activation of p53.