Biochemistry 2280A Lecture Notes - Lecture 21: Pyrimidine Dimer, Dna Mismatch Repair, Depurination
4 Apr 2016
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Dna damage: any unintended physical or chemical change in dna or its sequence. Dna molecules are huge and are prone to damage. To try to avoid changes in nucleoide sequence, cells have developed mechanisms for repairing dna damage. Dna polymerase makes an error about once every 107 nt. Mismatched bp, causing mutaion in one daughter double helix. Inserion or deleion of one or more bases, potenially causing a shit in reading frame. Result of unrepaired replicaion error: deaminaion. Spontaneous conversion of amine group to a carbonyl. Loss of enire g or a base, promoted by acid (sugar-phosphate backbone remains intact) Can be overcome by error-prone translesion dna polymerases (more likely to make mistakes) Since the template has no base, translesion dnap are likely to skip that posiion, or introduce mutaion. Ater translesion dnap goes past damage site, normal dnap resumes. Strand is intact but the base is lost. It will just put a random nt in there.
