Identification of human chromosomes by DNA-binding fluorescent agents.

The distribution of DNA along metaphase chromosomes that are not excessively contracted can be visualized in the fluorescence microscope with the aid of fluorescent DNA-binding agents. Additional, characteristic details in the fluorescence patterns are obtained with fluorochromes that bind preferentially to certain chromosomal regions. The highly fluorescent alkylating agent quinacrine mustard (QM) effects discrete, fluorescent labeling of both plant and mammalian metaphase chromosomes, presumably by selective binding to guanine residues in DNA, and is also capable of intercalation in the DNA double helix. Chromosome regions fluorescing particularly strongly with QM have been demonstrated in human metaphase chromosomes 3, 13–15 and Y.