BS 161 1st Edition Lecture 28 Outline of Last Lecture I DNA synthesis Outline of Current Lecture II DNA synthesis continued Current Lecture Problems during DNA replication The entire genome must be faithfully copied with exception of some mutation Already checked at G2 The replication must be synchronized with the cell s mitotic and cytokinetic events Already checked at M Unwinding and untwisting the helix creates torsion in the unreplicated portion which does not rotate DNA polymerase cannot start from ds or ss DNA and only makes DNA in 5 to 3 direction Proteins involved in DNA replication initiator finds ori helicase unwinds DNA helix breaks H bonds topoisomerase opens up DNA and prevents supercoils single strand DNA binding protein don t need to know function primase makes RNA sequence that DNA polymerase uses DNA polymerase Pol I and Pol III versions sliding clamp don t need to know function ligase seals the final phosphodiester bond DNA has complementarity and antiparallel structure review A T G C primase makes a short RNA complementary to the DNA sequence always goes in 5 C to 3 C direction DNA polymerase III matches appropriate monomer to template and makes the phosphodiester bond from the primer and DNA 3 OH terminus the DNA pol III can only make 5 to 3 bonds so the copied DNA must be made in short sections of DNA plus the primer Okazaki fragments
View Full Document
Unlocking...