pp 295 - 301. 2. replication elongation dna polymerase – enzyme which does what? in what...
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DNA Replication Elongationpp 295 - 301
2. Replication ElongationDNA polymerase – enzyme which does what? In what
direction? What is the main version responsible for replication?in prokaryotes: DNA polymerase I, II, III, IV & Vin eukaryotes: over 15 different types
Nucleotide chains only form in the 5’ 3’ direction.
DNA Polymerase III Substrates1. DNA template2. deoxyribonucleoside triphosphates (dNTPs)
3. RNA primer
5’3’
5’3’
5’ 3’
2. Replication Elongation1. Primase:
5’3’
5’ 3’
A
2. Replication ElongationThree steps involved in the addition of every
nucleotide to the new piece of DNA are:
AT
TTP P P
2. Replication Elongation
2. Replication ElongationIn what direction must the DNA polymerase produce
the new strand of DNA?
Which direction does the replication fork open?
2. Replication ElongationProkaryotic DNA is circular. Two DNA polymerases
replicated in opposing directions until both strands are completed.
2. Replication ElongationEukaryotic DNA is linear. DNA polymerases in travel
both directions from the ori site.
What direction is DNA synthesized?
Leading Strand
5’
5’
3’
3’
helicase
SSBPs
gyrase
primase
5’
3’
DNA polymerase III
Lagging Strand
Okazaki fragment
5’
3’
5’
3’
5’
3’
helicasegyrase
2. Replication ElongationOkazaki fragments:
DNA polymerase I –
DNA ligase –
2. Replication ElongationDNA replication occurs:
1. continuously on the _______ strand
2. discontinuously on the _______ strand
Replication Animation
3. Replication TerminationTelomeres
TTAGGG
Telomeres
TelomeraseExplain what happens to the telomere during each
round of replication, why this is important and why some cells have a mechanism to repair this while others do not…
TelomeraseTelomeres and aging?
TelomeraseTelomerase:
Mistakes in DNA ReplicationFewer than 1 error in 107 NTs
Exonuclease –
Roles of DNA polymerase I and II
ClassworkIntroduce yourself to your neighbor
Everyone get into groups of 2-3
In groups, summarize DNA replication as a series of steps