双链断裂修复模型 Double-strand break made in recipient Displaced strand migrates to other duplex ■■具■■■ Break is enlarged to gap with 3'ends DNA synthesis occurs from other 3'end HH 3'end migrates to other duplex Gap replaced by donor sequence Reciprocal migration generates double crossover Synthesis from 3'end displaces one strand in gap H 形成两个holliday?交叉双链断裂修复模型 3’ 形成两个holliday交叉