| Popis: |
The polar cap cells of Drosophila (early germ track cells) were posttreated with photoreactivating light after treatment with various doses of ultraviolet and the resulting lethal mutation rates compared with the rates induced by the same doses of ultraviolet in a nonposttreated series. In the nonposttreated, the dose-rate curve was found to rise rapidly at the lower doses employed, becoming less steep with increase in dose until it reaches a plateau, and finally falling off somewhat (these results confirming those earlier reported). By contrast, in the photoreactivated series, the dose-rate relationship appears best to fit a linear curve through the entire range of doses tested, the photoreactivated rates being well below those of the nonposttreated at the lower dosage ranges (0.7 plus or minus 0.4% versus 5.9 plus or minus 1.8% at the dose which shows the greatest difference), the difference in the rates getting less with increasing ultraviolet dose and the two rates (posttreated and nonposttreated) finally becoming much closer at the highest dose (2.5 plus or minus 0.8% versus 4.3 plus or minus 1.2%). These results would indicate that there is a difference in the nature of the photoreactivable and nonphotoreactivable parts of ultraviolet mutagenesis. (auth) |
