Excision of UV-Induced Pyrimidine Dimers

In the case of UV irradiation, it is possible to make a direct measurement of the induction and subsequent disappearance of what is considered to be the UV-induced lesion of principal biological importance—namely, the pyrimidine dimer (Setlow and Carrier, 1964 Regan et aL, 1968 Carrier and Setlow, 1971). The radiochromatographic technique used has been reviewed in detail recently (Carrier and Setlow, 1971). 

FIGURE 1. Assay of repair replication by cesium chloride centrifugation. Diagrammatic representation of the results of a typical experiment with normal and XP skin cells. Note new incorporation of H-BrUra into region where old (parental) DNA sediments in normal cells (lower left panel) this is not present in XP cells (lower right panel). 

The BrUra photolysis assay is rapid and sensitive it can detect one 

MOST DIMERS REMAIN. LITTLE BrdUrd INSERTED 

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