Using your knowledge of DNA repair pathways, choose the pathway that would be used to repair the following types of DNA damage. Explain your reasoning.

a double-stranded break that occurs during G₁ and prevents completion of DNA replication

Key Concepts

Double-Stranded Breaks (DSBs)

Double-stranded breaks are severe forms of DNA damage where both strands of the DNA helix are broken. This type of damage can lead to genomic instability if not repaired properly, as it can result in the loss of genetic information or chromosomal rearrangements. DSBs can occur due to various factors, including ionizing radiation, chemical agents, or during normal cellular processes like DNA replication.

Homologous Recombination (HR)

Homologous recombination is a critical DNA repair pathway that repairs double-stranded breaks using a homologous sequence as a template. This process is most active during the S and G₂ phases of the cell cycle when sister chromatids are available. HR is highly accurate, ensuring that the genetic information is restored correctly, which is essential for maintaining genomic integrity.

Non-Homologous End Joining (NHEJ)

Non-homologous end joining is a DNA repair mechanism that directly joins the broken ends of DNA without the need for a homologous template. This pathway is predominant in the G₁ phase of the cell cycle, making it particularly relevant for repairing double-stranded breaks that occur before DNA replication. While NHEJ is faster and more efficient, it can be error-prone, potentially leading to insertions or deletions at the repair site.