Measurement by flow cytometry of genomic AT/GC ratio and genome size

Flow cytometry with the AT‐specific fluorochrome Hoechst 33258 (HO) and the GC‐specific fluorochrome olivomycin (OM) was used for measurement of base pair specific DNA content in 20 species of vertebrates. The results were found to be in good correlation with the biochemical literature on base pair frequencies (r = 0.972, P < 1 × 10 −8 ). This correlation allows one to determine the percent of GC/AT‐pairs and genome size from flow cytometric data. The genome sizes obtained were compared with the literature data on flow cytometric genome size values determined with the use of propidium iodide (PI) that is usually believed to be non‐base pair specific. The results were found to be in general agreement; however, the previously reported slight GC‐preference of PI is confirmed. The optimal conditions for flow cytometry of AT/GC ratio and genome size with the use of OM and HO are discussed. The approach can be useful for research in ecology, fisheries science, species conservation, and other environmental studies as a tool for rapid survey of a vast array of specimens. © 1994 Wiley‐Liss, Inc.