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Unit 4 – Molecular Genetics (Ch. 5.2)
DNA Replication Unit 4 – Molecular Genetics (Ch. 5.2)
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DNA Replication DNA replication occurs in three phases:
Initiation phase: a portion of the DNA double helix is unwound to expose the bases for new base pairing. Elongation phase: two new strands of DNA are assembled using the parent DNA as a template. The new DNA molecules (composed of one parent strand and daughter strand) re-form into double helices. Termination phase: the replication process is completed and the two new DNA molecules separate from each other.
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Initiation origin of replication 5’ 3’ 3’ 5’
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Initiation helicase 3’ 5’ 3’ 3’ 5’ 5’
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Initiation SSBs SSBs SSBs helicase SSBs SSBs SSBs
single-strand-binding protein SSBs SSBs Initiation SSBs helicase 3’ 5’ replication fork replication bubble 3’ 5’ SSBs SSBs SSBs
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Elongation SSBs SSBs SSBs helicase SSBs SSBs SSBs DNA polymerase III
3’ 5’ leading strand 3’ 5’ SSBs SSBs SSBs
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Elongation SSBs SSBs SSBs helicase SSBs SSBs SSBs DNA polymerase III
3’ DNA polymerase III 5’ RNA primer Okazaki fragment lagging strand 3’ 5’ SSBs SSBs SSBs primase
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Elongation SSBs SSBs SSBs helicase SSBs SSBs SSBs DNA polymerase I
DNA ligase Elongation SSBs SSBs SSBs DNA polymerase III helicase 3’ 5’ 3’ 5’ SSBs SSBs SSBs
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Termination 5’ 3’ 5’ 3’
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Correcting Errors during DNA Replication
DNA polymerase II Correcting Errors during DNA Replication !!!!! mismatch repair template strand 5’ 3’ 3’ 5’ new strand exonuclease
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