A rapid modified fluorescence-plus-Giemsa technique for sister chromatid exchanges and DNA replication patterns.

Five different fluorochromes were tested, in a revised fluorescence-plus-Giemsa technique, for their ability to give good quality permanent preparations. Hoechst 33342 was found to give the best results. Slides were stained with Hoechst 33342, followed by exposure to long wavelength UV light with a simultaneous incubation in a hot alkaline solution, and then were Giemsa stained. This technique gives good quality preparations, in approximately 1 h, of sister chromatid exchanges or DNA replication patterns.