The tumor suppressor gene P53 induces cell arrest at
**Question:** The tumor suppressor gene P53 induces cell arrest at
A. G1 phase
B. G2 phase
C. G3 phase
D. M phase
**Correct Answer:** A. G1 phase
**Core Concept:** The tumor suppressor gene P53 plays a crucial role in maintaining genomic stability and preventing the development of cancer. It acts as a "guardian of the genome" and responds to various cellular stresses, such as DNA damage, oxidative stress, or oncogene activation.
**Why the Correct Answer is Right:** The tumor suppressor gene P53 induces cell cycle arrest at the G1 phase (Gap 1 phase) in response to cellular stress. This arrest allows cells to repair DNA damage or undergo apoptosis (programmed cell death) if the damage is irreparable. By preventing damaged cells from entering S phase (DNA synthesis) and mitosis (cell division), P53 helps prevent the propagation of genetic mutations that could lead to uncontrolled cell growth and the development of cancer.
**Why Each Wrong Option is Incorrect:**
B. The correct answer (A) pertains to the G1 phase, whereas option B refers to the G2 phase (Gap 2 phase). Although both G1 and G2 phases are involved in the cell cycle, the correct answer is specific to the G1 phase.
C. G3 phase (Gap 3 phase) is the third phase of the cell cycle, following S phase (DNA synthesis) and preceding mitosis. It is not the phase at which P53 induces cell cycle arrest.
D. M phase (Mitotic phase) is the final phase of the cell cycle, characterized by cell division. P53 does not induce cell cycle arrest at this phase; instead, it is involved in preventing cells from entering the M phase with damaged DNA.
**Clinical Pearls:**
1. The tumor suppressor gene P53 is often referred to as the "guardian of the genome" due to its crucial role in maintaining genomic stability and preventing cancer.
2. Understanding the function of P53 is essential for grasping the concept of cell cycle regulation and genomic integrity.
3. P53-related questions often test your knowledge of cell cycle regulation, DNA damage response, and the role of P53 in preventing genomic instability and cancer progression.