G2 checkpoint

Definition

The G2 checkpoint is a critical control mechanism in the cell cycle that occurs at the transition between the G2 phase and mitosis (M phase). This checkpoint ensures that DNA has been accurately replicated and that any damage to the DNA is repaired before the cell proceeds to divide. The G2 checkpoint plays a vital role in maintaining genomic integrity, preventing the propagation of damaged or incomplete genetic material.

5 Must Know Facts For Your Next Test

1. The G2 checkpoint assesses the completeness of DNA replication, ensuring that the cell does not enter mitosis with unreplicated or damaged DNA.
2. If errors are detected at the G2 checkpoint, the cell cycle can be halted, allowing for repair mechanisms to fix any issues before division occurs.
3. Proteins like p53 are crucial at the G2 checkpoint, as they help regulate the response to DNA damage and can trigger cell cycle arrest if necessary.
4. Successful passage through the G2 checkpoint is essential for cells to enter mitosis; failure to do so can lead to apoptosis or cancerous growth.
5. The G2 checkpoint is also influenced by external signals such as growth factors and stress conditions, which can impact the decision of a cell to proceed with division.

Review Questions

• How does the G2 checkpoint ensure genomic integrity before a cell enters mitosis?
  • The G2 checkpoint plays a crucial role in maintaining genomic integrity by monitoring DNA replication and repair. It checks whether all DNA has been accurately replicated and assesses any damage present. If problems are found, such as incomplete replication or DNA damage, the checkpoint halts the cell cycle, allowing time for repair mechanisms to act before the cell proceeds to mitosis. This prevents damaged or incomplete genetic material from being passed on to daughter cells.
• Discuss the consequences of failing to properly regulate the G2 checkpoint in cellular processes.
  • Failing to properly regulate the G2 checkpoint can lead to severe consequences, including the propagation of damaged DNA and genomic instability. When a cell bypasses this checkpoint without addressing issues, it can proceed to mitosis with unrepaired genetic material. This can result in mutations and chromosomal abnormalities, contributing to cancer development. Additionally, such dysregulation disrupts normal cellular processes and can lead to uncontrolled cell growth.
• Evaluate how external signals might influence the functioning of the G2 checkpoint in different cellular contexts.
  • External signals such as growth factors and stressors play a significant role in influencing how the G2 checkpoint functions. For example, growth factors may promote progression through the G2 checkpoint by signaling favorable conditions for division, while stressors like DNA damage or nutrient deprivation can activate pathways that lead to cell cycle arrest. This dynamic response allows cells to adapt their division strategies based on environmental conditions, ultimately affecting tissue homeostasis and responses to damage.

Related terms

Cell Cycle: The series of phases that a cell goes through from its formation until it divides, including G1, S, G2, and M phases.

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

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