An analysis of factors for the differential staining of sister chromatids in human chromosomes using Giemsa.

Various reagents were tested for the purpose of developing an improved Giemsa staining technique for the differential staining of sister chromatids in human chromosomes. Reagents like acids, bases, buffers, protein denaturants and proteolytic enzymes were all potent inducers of differential staining. The best results were obtained by brief trypsinization followed by extraction of nucleic acids by incubation in hot HCl. There was poor contrast between unifilarly and bifilarly BrdU substituted chromatids in slides from which trypsin treatment was omitted. The method of slide preparation as they affect the spreads of BrdU substituted metaphases were also evaluated. The results support the role of these reagents in the conformational changes and structural lesions of chromosomal protein leading to differential staining.