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DNA end resection, also called 5′–3′ degradation, is a biochemical process where the blunt end of a section of double-stranded DNA is modified by cutting away some nucleotides from the 5' end to produce a 3' single-stranded sequence. The presence of a section of single-stranded DNA allows the broken end of the DNA to line up accurately with a matching sequence, so that it can be accurately repaired.
Double-strand breaks can occur at any phase of the cell cycle causing DNA end resection and repair activities to take place, but they are also normal intermediates in mitosis recombination. Furthermore, the natural ends of the linear chromosomes resemble DSBs, and although DNA breaks can cause damage to the integrity of genomic DNA, the natural ends are packed into complex specialized DNA protective packages called telomeres that prevent DNA repair activities. Telomeres and mitotic DSBs have different functionality, but both experience the same 5′–3′ degradation process.