Double-strand breaks are repaired error-free by
Double-strand break is most cytotoxic lesion resolved by two major pathways. Non-homologous end joining rapidly ligates ends but can delete nucleotides. Homology-directed repair, also termed homologous recombination repair or HDR, uses sister chromatid present in late S and G2 phases as faithful template. After resection by MRN complex CtIP, Rad51 catalyzes strand invasion forming D-loop, polymerase delta extends using homologous sequence, Holliday junctions resolved. Because homologous donor retains exact original sequence, repair restores information without errors, essential for maintaining
Ref: Lodish Molecular Cell Biology 9th ed. Chapter 12: HDR error-free DSB repair; Alberts Ch.5 Homologous recombination precise repair