Final answer:
The p53 protein is the negative regulatory molecule that can trigger apoptosis when crucial cell cycle events fail, preventing the replication of damaged DNA to maintain genomic stability (option a).
Step-by-step explanation:
The negative regulatory molecule that can trigger apoptosis if vital cell cycle events do not occur is p53. This multifunctional protein plays a crucial role at the G1 checkpoint of the cell cycle. When damaged DNA is detected during the G1 phase, p53 halts the cell cycle and attempts to recruit enzymes to repair the DNA. If the DNA cannot be repaired, p53 is responsible for initiating apoptosis to prevent the replication of the damaged DNA. This action helps maintain genomic stability and prevents the potential development of cancerous cells.
Hence, the answer is option a.