BIOL 103 Lecture Notes - Lecture 1: Topoisomerase, Helicase, Dna Repair
Document Summary
If h bonds broken btw compl. strands. Form: 2 original, 2 new dna from original: a strand from original & newly synthesized. New strands: same base sequence/dna as originals. 1 new & 1 old strand has same sequence as 2 old/2 new. Starts at a spot where double strand is formed. When primer binds to a comple. sequence on ssdna. Direction of strand growth (begins with primer) depends on polarity of dna (5" & 3"end) Strand of dna always grows, add nucleotide to 3" end. Always grows from 5" to 3" direction. 3d shape of dna prevent it from being easily read, to make more dna. These structural features: prevent enzymes that make new dna (dna polymerase) from accessing the info dna. Requires breaking of dna-protein, double strand separates (unwinding) Prevent it from getting twist up to dysfunctional topography (topoisomerase) Dna polymerase: only add nucleotide to 3" and existing duplex. Primase: start rna chain de novo, add 5-10 nucleotides.