Reverse pattern in differential Giemsa staining of sister chromatids.

Abstract
Chinese hamster strain cells cultured with 20 .mu.M BrdU [5-bromodeoxyuridine] for 2 or 3 rounds of replication were routinely air-dried. The chromosome preparations were treated with 0.001% trypsin at room temperature for 5 to 10 s, or incubated in 0.1 M Na2HPO4 at 37.degree. C for 2 to 4 h. These preparations were then stained with alkaline Giemsa solution (1.5% in 0.1 M Na2HPO4) for 5 to 10 min. These procedures resulted in a reverse type of sister chromatid differential staining; darkly stained BB-chromatids and faintly stained TB-chromatids.