Practice question

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 genome stability and enabling precise genome editing applications using donor templates.