Lecture 5I. DNA Replication FactsA. Topoisomerase1. enzyme that supercoils to help with chromosome condensation to help package a large number of nucleotides into a tiny eukaryotic nucleusB. Chromosomes1. Eurayotes have histone protiens that have DNA wrapped around it2. DNA+Histone proteins=NucleosomesII. DNA ReplicationA. Initiation1. DNA is unwound by helicase(protein)i. breaks the hydrogen bonds between the base pairs2. Single Stamard DNA binding Proteins(SSBP)(Protien)- stabilizes the single strands3. Topoisomerase (protein) relaves the twisting forces of helicase to prevent DNA from tanglingi. breask and rejoins the DNA helix to relieve twistind forces caused by the opening of the helix4. Primase (Protein) synthesizes a RNA Primer on the leading strandB. Elongation1. DNA Polymerase III (Protein) comes behind the RNA primer and works in the 5’ to 3’ direction and this sythsize the leading strand1. phosphodiester bonds form between the new nucleootides2. Sliding Clamp(Protein) holds down DNA polymerase3. The leading the stand is synthesized conticously in the direction that the helicase unwinds DNA4. Synthesis of the Lagging strand in the 5’ to 3’i. Primase lays down several RNA primers ii. DNA Polymerase III sytheniszes Okazai Fragments of Lagging strandsiii. DNA polymerase I(Protein) removes ribonucleotides of primer andbrings in dntpsiv. DNA Ligaes (Protein) closes closes the gaps between the Okazgi fragmenst by re-establishing phosphodiester bonds between backbone on the lagging strandv. synthesis is discontiousC. Termination1. when the replication forks