Please can you explain me how the gap created by the removal of primer on 5'-3' leading strand is filled.
The group of cellular enzymes that remove RNA primers include the proteins FEN1 (flap endonuclease 1) and RNase H. The enzymes FEN1 and RNase H remove RNA primers at the start of each leading strand and at the start of each Okazaki fragment, leaving gaps of unreplicated template DNA. Once the primers are removed, a free-floating DNA polymerase lands at the 3' end of the preceding DNA fragment and extends the DNA over the gap. However, this creates new nicks (unconnected sugar-phosphate backbone).
In the final stage of DNA replication, the enyzme ligase joins the sugar-phosphate backbones at each nick site. After ligase has connected all nicks, the new strand is one long continuous DNA strand, and the daughter DNA molecule is complete.
Source: Boundless. “DNA Replication in Eukaryotes.” Boundless Biology. Boundless, 08 Jan. 2016. Retrieved 14 Mar. 2016 from https://www.boundless.com/biology/textbooks/boundless-biology-textbook/dna-structure-and-function-14/dna-replication-101/dna-replication-in-eukaryotes-437-12941/