Figure 8.

Diagram showing how the 3′-ssDNA tails of dsDNA substrates (generated by λ Exo acting on the dsDNA ends) could anneal to the ssDNA regions of a replication fork. The 3′-ssDNA tail on top (in green) anneals to an ssDNA region within the lagging strand template, while the 3′-ssDNA tail on bottom (in red) anneals to an ssDNA region within the leading strand template (a more infrequent event perhaps, due to lesser amounts of ssDNA expected on this template). In either case, the invading duplex becomes one prong of the new fork, with the annealed strand becoming the new lagging strand template.