A rapid method for identification of constitutive heterochromatin of secondary constriction regions of human chromosomes 1, 9, and 16.

The secondary constriction regions (h) of chromosomes 1, 9, and 16 stained deep red by RBA (R-bands by BrdU using Giemsa)--a useful tool for demonstrating the constitutive heterochromatic heteromorphisms in these regions. The unusual staining pattern of bands p 12 to q11 of chromosome 3, which is late replicating, also is reported. The extended deep red region does not correspond to C-banding on chromosome 3. This technique does not require sequential banding by QFQ and CBG for detecting the h-region heteromorphisms.