FIGURE 8.

Model for the release of the replication loop. Upon finishing the synthesis of an Okazaki fragment, the loop is released by dissociation of DNA polymerase from DNA rather than from the helicase. The lagging-strand DNA polymerase is retained at the replication fork for the synthesis of the next Okazaki fragment. The dissociation of DNA polymerase from a nick in DNA is easier than that from a single-stranded DNA gap, suggesting that loop release is triggered upon DNA synthesis reaching the 5′ terminus of the previously synthesized Okazaki fragment (collision model).