A pathway choice model for repair of a DNA DSB in Arabidopsis. Four different pathways for repairing a DNA DSB in diploid Arabidopsis cells are depicted. The thick arrows and windows indicate dominant pathways (C-NHEJ and HR-sister chromatids as templates) in WT cells. Disruption of either of the major pathways (such as by knocking out KU70 or SMC6B in this study) will promote a pathway switch. Depending on the stage of the cell cycle, NHEJ pathways are dominant in the G₁ phase, whereas HR pathways may be preferred in the S and G2 phases.