PathwayStep498 PathwayStep497 PathwayStep504 PathwayStep503 Formation of the Flap Intermediate Formation of Okazaki fragments Joining of adjacent Okazaki fragments Processive synthesis on the lagging strand Pubmed1671046 Reactome Database ID Release 4369183 Reactome, http://www.reactome.org ReactomeREACT_1385 The key event that allows the processive synthesis on the lagging strand, is polymerase switching from pol alpha to pol delta, as on the leading strand. However, the processive synthesis on the lagging strand proceeds very differently. DNA synthesis is discontinuous, and involves the formation of short fragments called the Okazaki fragments. During the synthesis of Okazaki fragments, the RNA primer is folded into a single-stranded flap, which is removed by endonucleases. This is followed by the ligation of adjacent Okazaki fragments. Removal of the Flap Intermediate