Biology 1001A Lecture Notes - Lecture 9: Pyrimidine Dimer, Dna Repair, Photolyase
16 Nov 2012
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Document Summary
Things move around in your genome, as though your genome was an ecosystem. A-t and g-c is most stable con guration therefore equilibrium favours one tautomer over another. Variance in ability to repair damage can contribute to differences among organisms of the same species. Some mutagens are tautomerically unstable base analogues. Thymine and uracil differ only in the presence of a methyl group. 5-bromouracil looks a lot like thymine to dna polymerase. 5-bromouracil is therefore considered a base analogue. This compound can be incorporated into dna by mistake. This compound is tautomerically unstable, which would cause increased tautomeric shifts and therefore increase the frequency of mutations. This is one mechanism by which chemicals can increase mutation frequency. Tautomeric shifts can occur without chemicals using physical mutagens. Uv radiation has enough energy to be absorbed by pyrimidine bases and rearrange parts of the atoms. One such rearrangement is the formation of thymine dimers which are two thymine molecules linked together.
