DNA REPLICATION MOLECULAR BIOLOGY – DNA replication, transcription.
F mechanism of DNA replication F practice questions LECTURE 13: DNA: STRUCTURE & REPLICATION II.
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Transcript of F mechanism of DNA replication F practice questions LECTURE 13: DNA: STRUCTURE & REPLICATION II.
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mechanism of DNA replication
practice questions
LECTURE 13: DNA: STRUCTURE & REPLICATION II
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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
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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'
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MECHANISM OF DNA REPLICATION DNA polymerase III (pol III) ... holoenzyme of 20+ subunits 1. polymerase catalyzes chain growth 5' 3'
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MECHANISM OF DNA REPLICATION prokaryotes have a single origin of replication bidirectional replication with 2 forks single terminus ~ 20 minutes (*... book says 40)
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MECHANISM OF DNA REPLICATION E. coli origin of replication tandem repeat consensus sequence protein binding sites
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MECHANISM OF DNA REPLICATION
replication to completion...
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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 ...
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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
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MECHANISM OF DNA REPLICATION DNA structure replication
enzymes functions
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MECHANISM OF DNA REPLICATION DNA structure
replication
5' 3'
enzymes functions
3'
5'
3'
5'
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MECHANISM OF DNA REPLICATION DNA structure
replication
5' 3'
phosphodiester bond
enzymes functions
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MECHANISM OF DNA REPLICATION helicases disrupt H-bonds binding strands of
DNA double helix
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MECHANISM OF DNA REPLICATION single-stranded binding proteins (SSBs) stabilize
DNA and prevent formation of duplex
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MECHANISM OF DNA REPLICATION topoisomerases relax supercoiling of DNA as
it unwinds... e.g., DNA gyrase
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MECHANISM OF DNA REPLICATION topoisomerases relax supercoiling of DNA as
it unwinds... e.g., DNA gyrase
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MECHANISM OF DNA REPLICATION DNA gyrase -
catalyzed supercoiling
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MECHANISM OF DNA REPLICATION DNA polymerase catalyzes replication 5' 3'
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MECHANISM OF DNA REPLICATION DNA polymerase catalyzes replication 5' 3' extends but cannot initiate replication ...
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MECHANISM OF DNA REPLICATION RNA primase enzyme
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MECHANISM OF DNA REPLICATION priming synthesis
primase enzyme
synth. short (~30 bp) RNA primer
primase + DNA + proteins = primosome
enzymes functions
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MECHANISM OF DNA REPLICATION primase + DNA + proteins = primosome
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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
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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
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MECHANISM OF DNA REPLICATION dimeric DNA pol III holoenzyme model
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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
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MECHANISM OF DNA REPLICATION telomerase has RNA template for making telomeres
telomere-specific DNAprobe (yellow)
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MECHANISM OF DNA REPLICATION enzyme summary...
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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
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PRACTICE QUESTIONS
you should be able to do
CH7, p. 250 # 1 - 25