G2 Checkpoint

Definition

The G2 checkpoint is a critical regulatory point in the cell cycle that occurs at the end of the G2 phase, just before the cell enters mitosis. This checkpoint ensures that the cell has successfully completed DNA replication and checks for any DNA damage, allowing the cell to proceed to division only if conditions are favorable. The G2 checkpoint is essential for maintaining genomic integrity and preventing the division of damaged or incomplete DNA.

5 Must Know Facts For Your Next Test

1. The G2 checkpoint assesses whether DNA has been correctly replicated and checks for any damage before allowing the cell to enter mitosis.
2. Proteins such as p53 play a crucial role in the G2 checkpoint by monitoring DNA integrity and can induce cell cycle arrest if damage is detected.
3. If the G2 checkpoint is passed, cyclin B binds to CDK1 (also known as cyclin-dependent kinase 1), which initiates the processes leading to mitosis.
4. Failure at the G2 checkpoint can lead to mutations and potentially contribute to cancer development due to unregulated cell division.
5. Research indicates that some cancer therapies aim to target the G2 checkpoint to enhance the sensitivity of cancer cells to treatment by forcing them into mitosis with unrepaired DNA.

Review Questions

• How does the G2 checkpoint ensure genomic integrity during the cell cycle?
  • The G2 checkpoint ensures genomic integrity by verifying that DNA replication has been completed accurately and checking for any DNA damage. If any issues are detected, such as incomplete replication or damaged DNA, the checkpoint can halt the cell cycle, allowing for repair mechanisms to take action before proceeding to mitosis. This process is crucial for preventing mutations from being passed on to daughter cells.
• Discuss the role of cyclins and CDKs in relation to the G2 checkpoint.
  • Cyclins and cyclin-dependent kinases (CDKs) play a vital role in regulating the progression through the G2 checkpoint. Specifically, cyclin B binds to CDK1 when conditions are favorable, leading to its activation. This activated complex then triggers events necessary for the transition into mitosis. Therefore, cyclins act as signals indicating readiness for cell division, while CDKs function as enzymes that drive this transition.
• Evaluate the implications of defective G2 checkpoint function in cancer therapy.
  • Defective G2 checkpoint function can have significant implications in cancer therapy since it allows damaged cells to continue dividing without repair. This can lead to tumor progression and metastasis. Targeting this checkpoint in cancer treatment could be beneficial; therapies might exploit this weakness by inducing stress on cancer cells that forces them into mitosis despite their unrepaired DNA. This strategy can increase cancer cell sensitivity to treatments like radiation or certain chemotherapies, aiming to improve patient outcomes.

Related terms

Cell Cycle: The series of stages that a cell goes through to grow and divide, including phases such as G1, S, G2, and M.

Mitosis: The process of cell division where one parent cell divides to produce two genetically identical daughter cells.

Cyclins: Regulatory proteins that control the progression of cells through the cell cycle by activating cyclin-dependent kinases (CDKs).