24 September, 2004

1
Chapter 9
Mutation and Repair

• 24 September, 2004

2
Overview

• DNA is replicated with high fidelity, but errors
  do occur.
• Errors during replication may be misincorporation
  or slippage.
• Errors that are not repaired by proofreading may
  be repaired my the mismatch repair systems.
• Mismatch repair systems rely on methylation to
  determine which base is correct.
• In addition to replication errors, DNA can be
  damaged by radiation, chemicals, or spontaneous
  reactions.
• DNA repair systems are specialized according to
  the type of damage they address.

3
Transitions and Transversions

4
Ratification of unrepaired errors

5
Mismatch Repair

6

7
Dam Methylation in E. coli
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Exonuclease activity exposes lesion
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DNA Damage
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Base Analogs and Intercalators
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Photoreactivation
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O6-Me-G repair
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Base excision repair
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Base excision repair
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Fail-safe systems
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Excision Repair
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Excision repair may be coupled to transcription.
18
Translesion Synthesis
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Ames Test
20
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