A, Schematic drawing of the EGFP-based SSA reporter, EGFP-SSA. The EGFP coding sequence is split into two fragments, which share a 315 bp overlapping homology (repeat) and are separated by a 2,035 bp DNA sequence. An I-SceI cleavage sequence is inserted in the intervening sequence, 9 bp away from the 3' repeat. The EGFP open reading frame is restored after DSB-induced RMD of the two EGFP fragments. 