Reverse differential staining of sister chromatids after substitution with BUdR and incubation in sodium phosphate solution

Abstract

Chinese hamster strain cells were cultured in the presence of BUdR and air-dried on slides. The chromosome preparations were incubated in 1 M NaH 2PO 4 at 88 °C for 4–6 min and stained with Giemsa. The reverse type of sister chromatid differential staining occurred, in which unifilarly BUdR-substituted chromatids stained faintly and bifilarly substituted chromatids stained darkly. Feulgen reaction performed on the same chromosomes after removing Giemsa stain showed the same type of differential staining.