Final answer:
Tumor cells can undergo apoptosis when irreparable DNA damage occurs and the p53 protein, which acts as a cell cycle checkpoint, fails to repair the DNA and subsequently initiates programmed cell death to prevent the damaged cells from proliferating.
Step-by-step explanation:
Tumor cells can undergo apoptosis if they have sustained DNA damage that is irreparable. The protein p53 plays a pivotal role in monitoring DNA integrity and ensuring cellular repair. When cellular damage occurs, p53 arrests the cell cycle until the damage is repaired. If the damage to the DNA cannot be fixed, p53 will initiate apoptosis to prevent the propagation of the damaged cells.
In the case of mutated p53 genes, which are identified in more than half of all human tumor cells, the damaged or faulty p53 may not properly detect errors or signal repair enzymes. Consequently, DNA damage remains uncorrected, and the dysfunctional p53 fails to trigger apoptosis, potentially leading to uncontrolled cell division and cancer formation. Thus, the presence of functional p53 is crucial in maintaining cellular integrity and preventing tumorigenesis by inducing apoptosis in cells with irreparable DNA damage.