Cytologic characterization of human constitutive heterochromatin

A study was conducted to cytologically map certain subsets of constitutive heterochromatin onto specific portions of human chromosomes. This involved sequentially staining metaphase chromosomes from lymphocytes first with the Centromeric Dot, Giemsa-11, G-banding or Lateral Asymmetry staining techniques, which are cytochemical methods which stain particular chromosomes or chromosomal regions. Then those same metaphase chromosomes were stained using the C-banding technique, a method which is believed to denote constitutive heterochromatin. With the exception of the G-banding technique, areas depicted by the special staining techniques were found to reside only within the areas stained by the C-band technique and are thus believed to be subsets of constitutive heterochromatin. In addition to portions of the C-band regions, G-banding stained regions throughout the chromosome arms but, only those residing within the C-band regions were considered to be subsets of constitutive heterochromatin. It was found that those regions identified by the Giemsa-11, Centromeric Dot and G-banding techniques were mutually exclusive of one another and occupied discrete regions within the C-bands.