Banding of unfixed mitotic chromosomes in suspension after release from human lymphocytes and fibroblasts

Combined application during chromosome isolation of the non- or weakly fluorescent DNA-intercalators 4'-aminomethyl-4,5',8-trimethylpsoralen and daunomycin as stabilizers of mitotic chromosome structure, and the non-intercalating DNA-binding fluorochromes DAPI and D287 /170 as producers of a visible banding pattern, resulted in clearly banded unfixed floating chromosomes. Chromosomes stabilized by intercalation appeared to be sufficiently stable to allow the reproduction of distamycin A/DAPI or netropsin/DAPI staining in suspension, thus highlighting specific heterochromatic regions on the floating chromosomes. The results of this study demonstrate that the inducibility of bands is an inherent characteristic of mitotic chromosome organization. Possible practical applications of these results in flow cytometry are discussed.