Classes of Mutations

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Classes of Mutations
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Consequences of mutations

• Base substitutions lead to nonsense, missense,
  neutral or silent mutations
• Frameshift mutations alter the translational
  reading frame
• Rearrangements reduce or eliminate protein
  function

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Methods for Inducing Mutagenesis
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Methods for Detecting Mutagenesis
Variety of test systems available that are based
on acquisition or loss of a specific genetic
marker, e.g. antibiotic resistance.
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UV-induced mutagenesis (using rif-resistance)

• Score for rifS to rifR.
• Rifampin (rif) targets the bacterial RNA Pol,
  blocking transcription.
• 69 possible single base substitutions confer rif
  resistance. These are concentrated in the first
  half of the protein, and are distributed among 24
  coding positions (Garibyan et al. DNA Repair 2
  (2003) 593-608).

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The strains
Wild-type strain -- provides reference for
frequency of mutation when repair and coping
systems are intact.
Excision repair mutant (uvrA) -- unable to remove
DNA lesions.
Mutant in damage-inducible DNA polymerase (umuC)
-- umuC allows mutagenic bypass of UV lesions.
Mismatch repair mutant (mutS) -- impairs removal
of mismatched base pairs that have passed through
proof-reading step of DNA replication
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UV irradiation and plating protocol
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Pull-down Assay