Bivariate Chromosome Analysis Using a Commercial Flow Cytometer

The bivariate analysis of human chromosomes in flow using the fluorochromes Hoechst 33258 (with specificity for AT-rich DNA) and Chromomycin A3 (with specificity for GC-rich DNA) was first described by Gray et al. in 1979 (1 ). Chromosomes stained with these two dyes can be resolved on the flow cytometer not only by their DNA content, but also by base pair ratio (see Fig. 1 ). Although other dye combinations have been used (e.g., refs. 2 –4 ), Hoechst and Chromomycin are the most widely used DNA fluorochrome pair for the bivariate analysis of human chromosomes.