to determine whether the time available for dna excision repair between ultraviolet irradiation ( 254 nm ) and the onset of dna synthesis was critical in determining the cytotoxic and/or mutagenic effect of uv in human fibroblasts , we released cultures of nf or xp12be cells from g0 , allowed them to reattach at lower densities , irradiated them in early g1 ( approximately 18 h prior to the onset of s ) or just prior to s phase , and assayed the frequency of mutations to 6-thioguanine resistance and the survival of colony-forming ability .
C0007634
cells
C0080129
s phase