Molecular and cell biology Lecture 2, Replication of DNA. Pt4 Replication of eukaryotic DNA
This video describes briefly replication of eukaryotic DNA. The replication occurs during the S phase of the cell cycle and duplicates the entire genome at thousands of origins of replication (ORs) to ensure timely completion. Initiation begins in G1 phase with the origin recognition complex (ORC) binding ORs, recruiting Cdc6 and Cdt1 to load the MCM helicase as the pre-replication complex (pre-RC); in S phase, Then, kinases activate MCM. MCM unwinds DNA with help from single strand binding proteins that stabilize unwound DNA. Elongation proceeds bidirectionally from each OR: DNA polymerase α-primase synthesizes short RNA-DNA primers, polymerase ε extends the leading strand continuously (5'→3'), while polymerase δ handles the lagging strand discontinuously as Okazaki fragments (~100-200 nt). After removal and degrading the primers, ligase I seals nicks for high-fidelity proofreading. Termination involves fork convergence, with telomeres replicated by telomerase to counter the end-replication problem.
This video describes briefly replication of eukaryotic DNA. The replication occurs during the S phase of the cell cycle and duplicates the entire genome at thousands of origins of replication (ORs) to ensure timely completion. Initiation begins in G1 phase with the origin recognition complex (ORC) binding ORs, recruiting Cdc6 and Cdt1 to load the MCM helicase as the pre-replication complex (pre-RC); in S phase, Then, kinases activate MCM. MCM unwinds DNA with help from single strand binding proteins that stabilize unwound DNA. Elongation proceeds bidirectionally from each OR: DNA polymerase α-primase synthesizes short RNA-DNA primers, polymerase ε extends the leading strand continuously (5'→3'), while polymerase δ handles the lagging strand discontinuously as Okazaki fragments (~100-200 nt). After removal and degrading the primers, ligase I seals nicks for high-fidelity proofreading. Termination involves fork convergence, with telomeres replicated by telomerase to counter the end-replication problem.