The Question is from neet-botany cell-cycle-and-cell-division interphase, and it was created by the author K SURESH KUMAR

Question

When cell has stalled DNA replication fork, which checkpoint should be predominantly activated?

K SURESH KUMAR · Accepted Answer

## CORE INFORMATION
✓ **Answer**: C
## CONCEPT FRAMEWORK
	**Primary Concept**: Cell Cycle Checkpoints
	**Related Topics**: DNA Replication, DNA Damage Response, Cell Cycle Regulation
	**Prerequisites**: Basic understanding of cell cycle phases (G1, S, G2, M) and the role of checkpoints in ensuring proper cell division.
## SOLUTION PATHWAY
**Given Information**:
	Stalled DNA replication fork.
	Goal is to identify the relevant cell cycle checkpoint.
**Method & Steps**:
	1. **Identify the problem**: A stalled replication fork indicates a problem during the S phase of the cell cycle when DNA is being replicated.
		Reasoning: DNA replication errors need to be corrected before cell division.
	2. **Determine relevant checkpoint**: The ${G_2}/M$ checkpoint is activated when there is DNA damage or stalled replication forks. It ensures that all DNA has been properly replicated before the cell enters mitosis (M phase).
		Reasoning: The G2 checkpoint is positioned to prevent damaged cells from dividing.
	3. **Evaluate other checkpoints**: While the M checkpoint checks for proper chromosome alignment during mitosis, and the G1/S checkpoint ensures that the cell is ready to enter S phase, neither are the primary controllers of replication fork stalling.
		Reasoning: The G1/S checkpoint prevents cells with insufficient resources from starting DNA replication.
**Final step**:
		Result: The G2/M checkpoint is the most relevant checkpoint for stalled DNA replication forks.
		Verification: Knowledge of checkpoint function supports this conclusion.
## OPTION ANALYSIS
[A] :x: While both G2/M and M checkpoints play a role in cell cycle progression, the primary response to a stalled replication fork occurs at the G2/M checkpoint. The M checkpoint is primarily concerned with chromosome alignment during mitosis.
[B] :x: The G1/S checkpoint ensures that the cell is ready to enter S phase. It's not directly related to monitoring ongoing DNA replication.
[C] ✓: The G2/M checkpoint is activated by DNA damage or replication problems, including stalled replication forks. This is the correct answer.
[D] :x: The M checkpoint focuses on ensuring chromosomes are properly attached to the spindle and aligned for division, not replication issues.
## LEARNING AIDS
	**Common Mistakes**:
		1. Confusing checkpoints: Not understanding the specific function of each checkpoint.
			How to avoid: Review the role of each checkpoint in the cell cycle.
		2. Associating all DNA issues with the same checkpoint: Not recognizing the specific checkpoint most relevant to replication issues.
			How to avoid: Understand the timing and function of each checkpoint.
	**Quick Tips**:
		1. Remember G2/M: Think of G2/M as the primary control gate for entering mitosis with the correct DNA.
		2. Associate S phase with G2/M: DNA replication occurs in S phase, and any errors will primarily be detected at the G2/M checkpoint.

K SURESH KUMAR · Answer

Both ${G_2}/M$ and M

K SURESH KUMAR · Answer

${G_1}/S$

K SURESH KUMAR · Answer

The correct Option is "${G_2}/M$"

K SURESH KUMAR · Answer

$M$

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