DNA repair base-excision repair Wikipedia:Base_excision_repair Reactome:R-HSA-73884 GO:0006284 Reactome:R-HSA-73930 BER In base excision repair, an altered base is removed by a DNA glycosylase enzyme, followed by excision of the resulting sugar phosphate. The small gap left in the DNA helix is filled in by the sequential action of DNA polymerase and DNA ligase. biological_process