Heterogeneity of human chromosome 9 constitutive heterochromatin as revealed by sequential distamycin A/DAPI staining and C-banding.

Distamycin A/DAPI staining and sequential C-banding of human lymphocyte chromosomes reveals the regular occurrence of differentially staining subfractions of chromosome 9 constitutive heterochromatin. These subfractions are regionally organized as two subsegments: a distal one, which fluoresces brightly with DAPI after preincubation with distamycin A and a proximal one, which stains intensely with Giemsa after sequential C-banding. Observations are presented that indicate an occasionally independent genetic behavior of these heterochromatin subfractions.