USA Biology Olympiad (USABO) Practice Exam

What is the primary role of the p53 gene in cancer biology?

1. Oncogene activation

2. DNA repair

3. Cell cycle regulation

4. Tumor suppressor

The correct answer is: Tumor suppressor

The p53 gene is primarily known as a tumor suppressor gene, which plays a critical role in preventing the development of tumors. It encodes a protein that is essential for regulating the cell cycle and maintaining genomic stability. When cellular stress is detected, such as DNA damage or abnormal cell growth, p53 becomes activated. It can induce cell cycle arrest, allowing the cell time to repair any DNA damage before proceeding with division. If the damage is too severe, p53 can promote apoptosis, or programmed cell death, thus preventing the propagation of potentially cancerous cells. The tumor-suppressing function of p53 is crucial in cancer biology because mutations in this gene often lead to a loss of its normal function. This loss allows damaged cells to proliferate uncontrollably, contributing to tumor formation and cancer progression. Thus, the primary role of p53 in cancer biology is indeed as a tumor suppressor, critical for maintaining normal cellular operations and preventing cancerous transformations.