BIOLOGY 172 Lecture Notes - Lecture 17: Dna Replication, Helicase, Okazaki Fragments
Document Summary
Break hydrogen bonds between the bases, exposing the bases in both strands. Dna helicase - enzyme that breaks the hydrogen bonds between the bases; separated 2 dna strands. Topoisomerase - cleaves both strands off, hangs on, allows them to unwind, then allows the strands to come back to original strand. Rna primer - small stretch of rna (10-15 nucleotides) complementary to the dna template. Rna primer is only to put a 3" side so dna polymerase can have a place to start polymerizing. Dna polymerase works in 5" to 3" direction, synthesizes the leading strand. Next nucleotide is added to 3" end always. Overall dna synthesis (in the slide) is from left to right (unzips) Primase adds rna primer and dna is synthesized from 3" end. But then there is a gap as the dna continues to unzip . Keeps adding rna primers to fill in gap segments. Okazaki fragments - short fragments of newly replicated dna on lagging strand.
