Localization of Sister Chromatid Exchanges in Human Chromosomes

The bromodeoxyuridine; sensitivity of 33258 Hoechst fluorescence allows microfluorometric analysis of sister chromatid exchanges in human metaphase chromosomes. The frequency of sister chromatid exchanges among chromosomes correlates with chromosome length. Exchanges appear to occur predominantly in interband regions, as defined by quinacrine fluorescence, or very near band-interband junctions. A few regions are involved unusually frequently.