Fluorescent DNA probes for flow cytometry. Considerations and prospects.

Techniques employing base specific deoxyribonucleic acid (DNA)-binding fluorochromes and flow cytometry (FCM) are potentially useful for obtaining information of the compositional features of chromatin or chromosomes of mammalian cells. Fluorescent compounds which form complexes preferentially at the A-T rich regions (i.e., DNA-reactive Hoechst dyes) or the G-C rich regions (i.e., mithramycin, chromomycin, olivomycin) in DNA are available and compatible with current FCM technology as are other compounds (i.e., ethidium bromide, propidium iodide) which show little or no base specificity and bind by intercalation in the double stranded regions of helical DNA. Energy transfer between appropriate DNA-bound dyes is a reflection of the quantity and proximity of regions containing the respective base pair segments. Since extrinsic fluorescent probes provide only a measure of available binding sites or regions unobstructed by chromatin-associated or chromosomal-associated proteins, interpretations of fluorescence measurements need to be substantiated by adequate control measures.