BIOL 141 Lecture Notes - Lecture 20: Dont, Telomere, Helicase
7 Dec 2017
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Document Summary
Nucleic acid synthesis only in 5" to 3" direction. A lot of dna (3. 2x109 base pairs in the human genome) Synthesis on both strands simultaneously with leading and lagging strand, both synthesized in 5" --> 3" direction. Each origin has a bidirectional replication bubble that fuse once they reach each other. Topoisomerase relieves upstream tension from winding to prevent tangles by clipping sugar-phosphate backbone. Dna polymerase proof-reads sequence to correct errors and remove rna. Corrects errors and also can remove and replace rna. Needs a 3" oh to hold on to. Ligase then fixes the nicks in the backbone. Dna polymerase needs a 3" -oh group to add to. Rna primers at the beginning of every fragment (leading strand and okazaki fragments of lagging strand) by primase need the 3" oh to start with. More evidence that rna was the first macromolecule.
