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

Verified step by step guidance

1. <span>Identify the type of DNA damage that has occurred during the S phase. Common types include single-strand breaks, double-strand breaks, and base mismatches.</span>
2. <span>Activate the appropriate DNA repair pathway. For example, base excision repair (BER) for small, non-helix-distorting base lesions, nucleotide excision repair (NER) for bulky helix-distorting lesions, or homologous recombination (HR) and non-homologous end joining (NHEJ) for double-strand breaks.</span>
3. <span>Recruit repair proteins to the site of damage. This involves signaling pathways that detect the damage and mobilize repair enzymes to the affected DNA region.</span>
4. <span>Repair the DNA damage using the selected pathway. For instance, in homologous recombination, the repair process uses a homologous sequence as a template to accurately repair the break.</span>
5. <span>Verify the integrity of the repaired DNA. The cell cycle checkpoints, particularly the G2/M checkpoint, ensure that the DNA is correctly repaired before the cell proceeds to mitosis.</span>

Key Concepts

DNA Damage Response (DDR)

The DNA Damage Response is a complex network of cellular pathways that detect and repair DNA damage. When DNA is damaged, particularly during the S phase of the cell cycle, DDR mechanisms are activated to halt the cell cycle, allowing time for repair processes to occur. This ensures that cells do not proceed to mitosis with damaged DNA, which could lead to mutations or cell death.

DNA Repair Mechanisms

Cells utilize several DNA repair mechanisms to fix damage, including base excision repair, nucleotide excision repair, and homologous recombination. Each mechanism is tailored to address specific types of DNA damage. For instance, homologous recombination is particularly important for repairing double-strand breaks, which can occur during DNA replication in the S phase.

Cell Cycle Checkpoints

Cell cycle checkpoints are regulatory pathways that monitor the integrity of the cell's DNA and ensure that the cell is ready to proceed to the next phase of the cycle. The G2/M checkpoint is crucial as it assesses DNA damage before mitosis. If damage is detected, the checkpoint can delay the cell cycle, allowing for repair processes to take place, thus preventing the propagation of damaged DNA.