C-bands in seven cases of accessory small chromosomes.

The C-bands of two cases of familial, genetically inactive, accessory small chromosomes and five cases of genetically active chromosomes were examined. Inactive chromosomes consist of constitutive heterochromatin and satellites only. In active chromosomes, euchromatin was present. These chromosomes contained two, one or no C-bands, although all these chromosomes were morphologically monocentric. C-banding is more informative than other banding methods for this category of chromosomes.