G2 phase

Definition

The G2 phase is a crucial part of the cell cycle that occurs after DNA synthesis (S phase) and before mitosis (M phase). During this phase, the cell undergoes final preparations for division, ensuring that all DNA is accurately replicated and that the cell is ready for mitosis. Additionally, checkpoints in this phase help assess any DNA damage, making it essential for maintaining genomic integrity.

5 Must Know Facts For Your Next Test

1. The G2 phase typically lasts for several hours to a few days, depending on the type of cell and its conditions.
2. During G2, the cell checks for DNA damage and repairs any issues before proceeding to mitosis, which helps prevent the propagation of mutations.
3. G2 includes an important checkpoint called the G2/M checkpoint, which ensures that all DNA is replicated and intact before mitosis begins.
4. If DNA damage is detected during the G2 phase, the cell can either repair it or trigger programmed cell death (apoptosis) to eliminate potentially harmful cells.
5. Cells that are more radiosensitive often show increased damage during G2 due to their preparations for division, making this phase critical in understanding radiation effects.

Review Questions

• How does the G2 phase contribute to genomic integrity during the cell cycle?
  • The G2 phase plays a significant role in maintaining genomic integrity by allowing cells to check for DNA damage that may have occurred during DNA replication in the S phase. The presence of checkpoints during G2 ensures that any issues can be addressed before the cell enters mitosis. This process not only helps repair damaged DNA but also prevents mutations from being passed on to daughter cells.
• Discuss how variation in radiosensitivity during the G2 phase can affect treatment outcomes in radiation therapy.
  • Variation in radiosensitivity during the G2 phase is important because cells are particularly vulnerable to radiation damage as they prepare for division. If cancer cells are more sensitive at this stage, radiation therapy can be more effective by targeting these cells when they are less capable of repairing damage. Understanding this sensitivity allows clinicians to optimize treatment timing and dosage to maximize tumor cell kill while sparing normal tissues.
• Evaluate strategies that could enhance the effectiveness of radiation therapy by manipulating the G2 phase in cancer cells.
  • To enhance radiation therapy effectiveness, strategies such as using drugs that specifically target the G2/M checkpoint can be employed. These drugs may inhibit checkpoint proteins, causing cancer cells to enter mitosis with unrepaired DNA damage, leading to increased cell death. Additionally, scheduling radiation treatment at times when tumor cells are predominantly in G2 can maximize their radiosensitivity, improving therapeutic outcomes while minimizing harm to normal tissues.

Related terms

Cell Cycle: The series of phases through which a cell passes to grow and divide, including G1, S, G2, and M phases.

Checkpoints: Control mechanisms in the cell cycle that assess whether the processes at each phase have been accurately completed before the cell proceeds to the next phase.

Mitosis: The process of cell division where replicated chromosomes are separated into two new nuclei, resulting in two genetically identical daughter cells.