Figure 6. Models of target-substrate structures.

(A) When the segment of the target molecule being deleted is larger than the segment being inserted, the target must bend to permit target-substrate annealing. For short insertions, this reaction has higher recombination efficiency, suggesting that the genome more easily adopts a favorable structure. (B) When a recombineering substrate directs an insertion without concomitant deletion, the substrate must bend to achieve target-substrate annealing. The flexibility of the substrate is likely to influence the stability of recombineering heteroduplex intermediate. The green arrow indicates the direction of DNA replication fork movement.