8_Repair

Lehninger Principles of Biochemistry

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Unformatted text preview: Lecture 8: DNA Damage & Repair • Chemical reactions and some physical processes constantly damage genomic DNA – At the molecular level, damage usually involves changes in the structure of one of the strands – Vast majority are corrected by repair systems using the other strand as a template – Some base changes escape repair and the incorrect base serves as a template in replication – The daughter DNA carries a changed sequence in both strands; the DNA has been mutated • Accumulation of mutations in eukaryotic cells is strongly correlated with cancer; most carcinogens are also mutagens Types of DNA Repair Systems • Mismatches arise from occasional incorporation of incorrect nucleotides • Abnormal bases arise from spontaneous deamination reactions or via chemical alkylation • Pyrimidine dimers form when DNA is exposed to UV light • Backbone lesions occur from exposure to ionizing radiation Reading 8| pp. 289-292 25 | pp. 993-1016 © 2009 W. H. Freeman and Company ...GACTTAGAA......
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8_Repair - Lecture 8: DNA Damage & Repair • Chemical...

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