Sister chromatid differential staining by direct staining in Na2HPO4-Giemsa solution and the mechanism involved

Abstract

The direct staining of BrdU-substituted Chinese hamster chromosomes in a Na₂HPO₄-Giemsa solution without any pretreatments resulted in a B-dark type SCD in which bifilarly substituted (BB) chromatids stained dark and unifilarly substituted (TB) chromatids stained light. Detailed examinations of the staining process suggested that the Na₂HPO₄ solution acts to collapse chromosomes whereas the Giemsa dye works to reconstruct the collapsed chromosomes, and that during the reconstruction process preferential binding of the Giemsa dye to the BB-chromatids occurs to produce the B-dark SCD. It was revealed that not only the time but the temperature at which chromosome preparations are kept prior to use considerably affect the occurrence of SCD.