BIOB11H3 Lecture Notes - Lecture 14: Okazaki Fragments, Dna Clamp, Dna Replication
Document Summary
Licensing - permit to do something/mechanism that ensures that replication occurs only once per cell cycle. Primase - initiates dna replication (type of rna polymerase, synthesizes short. Rna primer that provides 3" hydroxyl group that dna polymerase needs) Figure 13. 12: movement of helicase is from right to left, helicase unwinds dna and primase moves alongside = primosome. Adding nucleotides in 5" - 3" by primase as helicase opens the strand from right to left = leading strand. Lagging strand produced by dna polymerase (anti parallel) Replication fork - bidirectional synthesis by polymerase molecules produces these forks: polarity is reversed (leading vs. lagging) -> looping of 1 of 2 strands, 180 from its original position. Figure 13. 14: 2 dna pol, 2 clamps held to template strands, associated with heximer (6 mol. of dna helicase), clamp loader = resp. for release of lagging strand template. Figure 13. 15: take up strand again, bind to beta clamp, synthesize the next okazaki fragment.
