BISC 202 Lecture Notes - Lecture 24: Dna Replication, Helicase, Transfer Rna
Document Summary
Topoisomerase moves in advance of helicase to relive strain on the dna double strand: helicase unwinds the double strand of dna, forming a replication fork. Single stranded binding proteins bind to the dna strands to prevent re-attaching. Rna primase synthesizes a primer on the 3"end of each template strand to provide an initiation point for dna polymerase iii: dna polymerase iii starts adding nucleotides to the template strand according to the complementary base-pairing rule. Dna pol iii moves in the 3" to 5" direction, it moves toward the replication fork on the leading strand and away from the fork on the lagging strand. New dna strand is being formed in the 5" to 3" direction. Rna primase synthesizes more rna primers on the lagging strand. However, the hairpin loop structure is in its way, rna pol has no option but stops transcribing. No post-transcriptional modi cations, transcription and translation happen at the same time in prokaryotes.