Abstract
Chinese hamster strain cells cultured with 20μM BrdU for two or three rounds of replication were routinely air-dried. The chromosome preparations were 1) treated with 0.001% trypsin at room temperature for 5 to 10s, or 2) incubated in 0.1M Na2HPO4 at 37°C for 2 to 4h. Then, these preparations were stained with alkaline Giemsa
solution (1.5% in 0.1M Na2HPO4) for 5 to 10min. These procedures resulted in a reverse type of sister chromatid differential staining; darkly stained BB-chromatids and faintly stained TB-chromatids.
