3 4 radiation and mutagenesis uv crosslinking

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Unformatted text preview: to cause cancer. 3 4 Radiation and mutagenesis: UV crosslinking produces pyrimidine dimers Example: Cancer DNA damage is ongoing and cumulative These lesions probably account for most cases of skin cancer – the most common cancer in the United States. Depurination (base loss): 20,000/cell/day Deamination: 100/cell/day About 1/1000 of the genome in each human cell is damaged per year. DNA photolyase (not in humans) If you live to age 80, that’s ~10% of the genome in each cell. hv UV-A or -B nucleotide excision repair American Academy of Dermatology And as we age, the repair machinery becomes less e cient. 6 5 Radiation and mutagenesis: DNA photolyase: a remarkable solar-powered enzyme that repairs cyclobutane thymine dimers Nucleotide excision repair System recognizes helix (backbone) distortions, not speci c chemical groups or adducts. Repairs UV photoproducts, among other lesions 1. MTHF is a “photon antenna” that absorbs UV-A and gets as photoexcited as a Sea leite on a sunny day = ABC excin...
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