If a cell suffers damage to its DNA while in S phase, how can this damage be repaired before the cell enters mitosis?

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Understand that the S phase is the part of the cell cycle where DNA replication occurs, so the DNA is being copied and is more vulnerable to damage.

Recognize that cells have specific DNA damage repair mechanisms active during S phase, such as the homologous recombination repair pathway, which uses the sister chromatid as a template for accurate repair.

Identify that the cell cycle has checkpoints, particularly the G2/M checkpoint, which monitors DNA integrity after replication and before mitosis to prevent progression if damage is detected.

Explain that if DNA damage is detected during S phase or G2, the cell cycle can be temporarily halted to allow repair mechanisms to fix the damage before mitosis begins.

Summarize that the combination of DNA repair pathways (like homologous recombination) and cell cycle checkpoints ensures that DNA damage incurred during S phase is repaired before the cell enters mitosis, maintaining genomic stability.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

DNA Damage and Repair Mechanisms

Cells have specialized pathways to detect and repair DNA damage, such as base excision repair, nucleotide excision repair, and homologous recombination. These mechanisms ensure genomic integrity by correcting errors before cell division.

S Phase and DNA Replication

The S phase is the part of the cell cycle where DNA is replicated. During this phase, the cell is particularly vulnerable to DNA damage, but also has active repair systems to fix errors before replication completes and the cell progresses to mitosis.

Cell Cycle Checkpoints

Checkpoints are control mechanisms that monitor and regulate the progression of the cell cycle. The G2/M checkpoint ensures that DNA damage is repaired after S phase and before mitosis, preventing the division of cells with damaged DNA.

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