Origin recognition ORC,MCM proteins helicase activity, ssDNA RPA, Primer synthesis polymers alpha/primase,Sliding clamp PCNA, primer removal RNase H, FEN1.Pol α/Primase synthesizes an RNA chain of 10 nucleotides followed by another 20 nucleotides of initiator DNA (iDNA). Because Pol α/Primase has no proofreading ability, this whole section of RNA/iDNA is removed. The exonucleases RNase H removes the RNA and Fen1 removed the iDNA. The gap is filled in by Pol δ and DNA ligase joins the 2 ends.Eukaryotic DNA Replication All have 5’ to 3’ Polymerase activity.