In the short flap pathway in eukaryotes the lagging strand of DNA is primed in short intervals. In the short pathway only, the nuclease FEN1 is involved. Pol δ frequently encounters the downstream primed Okazaki fragment and displaces the RNA/DNA initiator primer into a 5′ flap. The FEN1 5’-3’ endonuclease recognizes that the 5’ flap is displaced, and it cleaves, creating a substrate for ligation. In this method the Pol a-synthesized primer is removed. Studies show that in the FEN1 suggest a ‘tracking; model where the nuclease moves from the 5’ flap to its base to preform cleavage. The Pol δ does not process a nuclease activity to cleave the displaced flap. The FEN1 cleaves the short flap immediately after they form. The cleavage is inhibited when the 5’ end of the DNA flap is blocked either with a complementary primer or a biotin-conjugated streptavidin moiety. DNA ligase seals the nick made by the FEN1 and it creates a functional continuous double strand of DNA. PCNA simulates enzymatic functions of proteins for both FEN1 and DNA ligase. The interaction is crucial in creating proper ligation of the lagging DNA strand. Sequential strand displacement and cleavage by Pol δ and FEN1, respectively, helps to remove the entire initiator RNA before ligation. Many displacements need to take place and cleavage reactions are required to remove the initiator primer. The flap that is created and processes and it is matured by the short flap pathway.