Nature of the longitudinal differential staining of metaphase chromosomes

Patterns of differential longitudinal spiralization of chromosomes induced by the addition of 5-bromodexyuridine (200 mug/ml) for 5-7 h before fixation of the cells were compared with the differential staining of normally spiralized chromosomes with giemsa stain in chromosomes of lymphocytes in human blood cultures. The patterns of differentiation of both types were found to coincide for all chromosomes of the normal karyotype; areas of incomplete spiralization corresponded to areas staining intensively with giemsa stain. The significance of these results in connection with the mechanisms of differential staining of metaphasechromosomes is discussed.