DNA repair in the variable platyfish (Xiphophorus variatus) irradiated in vivo with ultraviolet B light

Dark- and light-dependent DNA repair processes were studied in vivo in the variable platyfish, Xiphophorus variatus. Excision (dark) repair of the (6-4) photoproduct was more efficient than that of the cyclobutane dimer with approximately 70% of the (6-4) photoproducts removed by 24 h post-UVB radiation compared to approximately 30% of the cyclobutane dimers. Exposure to photoreactivating light resulted in rapid loss of most (> 90%) of the cyclobutane dimers and increased excision repair of the (6-4) photoproduct. Preexposure to photoreactivating light 8 h prior to UVB radiation increased the rate of photoreactivation two-fold.