Discussion section3

Discussion section3 - Discussion section#3 DNA replication...

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Unformatted text preview: Discussion section #3 DNA replication and DNA repair 04/21/08 DNA polymerases in eukaryotes α δ ε 3’ 5’ exonuclease → No Yes Yes Associates with primase Yes No No Requires PCNA no yes no processivity moderate high high Polymerase for lagging strand DNA repair Polymerase for leading strand no exonuclease only 100nt processive associates tightly with primase δ very processive (with PCNA, the clamp) 3’-5’ exonuclease but no primase ε very processive 3’-5’ exonuclease for UV damage Prokaryotes v.s. Eukaryotes speed: 1000nt /s Length of DNA: 4.6 x 10 6 One origin only(oriC) speed: 50 nt /s more DNA: 3 x 10 9 Multiple origins(replicons):every3-300kb Primer removal requires more than one enzymes(eukaryotes) 5’-3’ exonuclease DNA sequences required for eukaryotic chromosome replication =>identified by complementation system 1. An element required for replication: ARS (autosomal replicating sequence)=>replication origin 1. An element for segregation: The Centromere => required for chromosome segregation during mitosis 1. Linear DNA requires telomere sequences at the ends for stable replication +ARS +CEN Telomeres TTAGGG repeats (humans and other vertebrates) at end of chromosomes A few hundred (yeast) to a few thousand (vertebrates) base pairs. The 3’-end of the telomere extends 12-16 bp beyond the 5’ end of the complementary strand. Proteins bind to telomeres to protect the ends of chromosomes. Telomeres prevent chromosomes from getting shortened. Telomeres shortening is prevented by the action of telomerase . How does telomerase work? • http:// faculty.plattsburgh.edu/donald.slish/Telomerase.html Telomeres from G-quartets Hoogsteen-type base pairing Telomeric oligonucleotide: d(GGGGTTTTGGGG) •Guanine-rich polynucleotides will tend to aggregate via Hoogsteen- type base pairing and then to form cyclic tetramers known as G- quartets. • The G-rich strands of telomeres fold back on themselves to form a hairpin, two of which associate in an antiparallel fashion to form stable complexes of stacked G-quartets....
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This note was uploaded on 10/30/2010 for the course CHEM 114C taught by Professor Alexanderhoffmann during the Spring '08 term at UCSD.

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Discussion section3 - Discussion section#3 DNA replication...

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