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mechanism of DNA replication
practice questions
LECTURE 13: DNA: STRUCTURE & REPLICATION II
MECHANISM OF DNA REPLICATION
DNA replication requirements... 1. H bonds between bases must be broken 2. chain separation/unwinding 3. available pools of 4 dNTPs: A = T, C G 4. enzymes
E. coli... ~4.7 × 107 bp (47,000,000) molecule has ~ 4.7 × 106 turns (10 bp/turn) 1500 bp/s, ~ 20 min to divide with 1 origin
MECHANISM OF DNA REPLICATION DNA polymerase I (pol I)... several types of activity 1. polymerase catalyzes chain growth 5' 3' 2. exonuclease removes mismatches 3' 5' 3. exonuclease degrades double stranded DNA 3' 5'
MECHANISM OF DNA REPLICATION DNA polymerase III (pol III) ... holoenzyme of 20+ subunits 1. polymerase catalyzes chain growth 5' 3'
MECHANISM OF DNA REPLICATION prokaryotes have a single origin of replication bidirectional replication with 2 forks single terminus ~ 20 minutes (*... book says 40)
MECHANISM OF DNA REPLICATION E. coli origin of replication tandem repeat consensus sequence protein binding sites
MECHANISM OF DNA REPLICATION
replication to completion...
MECHANISM OF DNA REPLICATION eukaryotes have multiple origins of replication bidirectional replication with 2 forks 1.4 h (yeast) to 24 h (cultured animal cells)... or more issues...
linear vs circular coordination of multiple chromosomes
pulse/chase and autoradiography ...
MECHANISM OF DNA REPLICATION eukaryotes have multiple origins of replication bidirectional replication with 2 forks 1.4 h (yeast) to 24 h (cultured animal cells)... or more issues...
linear vs circular coordination of multiple chromosomes
pulse/chase and autoradiography ... Drosophila
MECHANISM OF DNA REPLICATION DNA structure replication
enzymes functions
MECHANISM OF DNA REPLICATION DNA structure
replication
5' 3'
enzymes functions
3'
5'
3'
5'
MECHANISM OF DNA REPLICATION DNA structure
replication
5' 3'
phosphodiester bond
enzymes functions
MECHANISM OF DNA REPLICATION helicases disrupt H-bonds binding strands of
DNA double helix
MECHANISM OF DNA REPLICATION single-stranded binding proteins (SSBs) stabilize
DNA and prevent formation of duplex
MECHANISM OF DNA REPLICATION topoisomerases relax supercoiling of DNA as
it unwinds... e.g., DNA gyrase
MECHANISM OF DNA REPLICATION topoisomerases relax supercoiling of DNA as
it unwinds... e.g., DNA gyrase
MECHANISM OF DNA REPLICATION DNA gyrase -
catalyzed supercoiling
MECHANISM OF DNA REPLICATION DNA polymerase catalyzes replication 5' 3'
MECHANISM OF DNA REPLICATION DNA polymerase catalyzes replication 5' 3' extends but cannot initiate replication ...
MECHANISM OF DNA REPLICATION RNA primase enzyme
MECHANISM OF DNA REPLICATION priming synthesis
primase enzyme
synth. short (~30 bp) RNA primer
primase + DNA + proteins = primosome
enzymes functions
MECHANISM OF DNA REPLICATION primase + DNA + proteins = primosome
MECHANISM OF DNA REPLICATION leading & lagging strand
replication is 5' 3'
replication moves along template 3' 5'
DNA pol III most synthesis
DNA pol I fills gaps on lagging strand
DNA ligase seals gaps
MECHANISM OF DNA REPLICATION replication fork
lagging strand
a) RNA primer growth
b) DNA elongation as Okazaki fragments
c) RNA primer removed by DNA pol I
d) DNA ligation
MECHANISM OF DNA REPLICATION dimeric DNA pol III holoenzyme model
MECHANISM OF DNA REPLICATION
chromosome ends
leading strand has no problem...
lagging strand cannot add RNA primer at end... leaving gaps
telomeres = DNA repeats made by...
telomerase
MECHANISM OF DNA REPLICATION telomerase has RNA template for making telomeres
telomere-specific DNAprobe (yellow)
MECHANISM OF DNA REPLICATION enzyme summary...
MECHANISM OF DNA REPLICATION
you should know names and functions of:
topoisomerase (e.g., DNA gyrase) single-stranded binding proteins (SSBs) DNA helicase DNA pol I DNA pol III DNA pol III holoenzyme RNA primer RNA primase
primosome Okazaki fragment DNA ligase telomerase
PRACTICE QUESTIONS
you should be able to do
CH7, p. 250 # 1 - 25
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