Cytochemical heterogeneity of the C-band in human chromosome 1.

The heterogeneity of the C-band of human chromosome 1 has been evaluated using several selective staining methods: C-banding (CBG), distamycin A plus 4-6-diamidino-2-phenylindole (DA/DAPI) and Giemsa G-11 pattern following the treatment with the restriction endonucleases AluI and HaeIII. The bands produced by each method are characteristic but not identical. The total C-band is resistant to AluI treatment. The bands induced by HaeIII and the one stained by DA/DAPI are markedly similar but smaller than the C-band. The G-11 technique stains yet smaller regions than those of HaeIII and DA/DAPI. Depending on the expression of staining properties, the C-band of chromosome 1 usually consists of three subdivisions: the proximal, intermediate and distal regions, suggesting an extremely heterogeneous nature. The staining variations between different regions are further substantiated by studies of a reciprocal translocation where the proximal region and the remaining C-band of chromosome 1 are separate.