Mechanisms of chromosome banding. IX. Are variations in DNA base composition adequate to account for quinacrine, Hoechst 33258 and daunomycin banding?
Abstract
Prior studies on subfractions of mouse and Kangaroo rat DNA have suggested that variations in base concentration within a given genome may not be great enough to account for Q-banding. To examine this with another species, calf DNA was subfractionated by CsCl ultracentrifugation into GC-rich satellites and the main band DNA was further fractionated into AT-rich, intermediate and GC-rich portions. The effect of varying concentrations of these DNAs on quinacrine and Hoechst 33258 fluorescence was examined. Although with both compounds there was less fluorescence in the presence of the GC-rich satellites than main band fractions, these results per se did not answer the question of whether the variation in base composition alone was adequate to account for chromosome banding. To answer this the fluorescence observed in the presence of DNA of a given base composition was related to the fluorescence observed in the presence of DNA of 40% GC content (F/F40). This allowed the derivation of a term B which indicated the relative change in fluorescence per 1% change in base composition of DNA. To determine the percent change in fluorescence observed in Q-banding, the photoelectric recordings of Caspersson et al. (1971) were used. From the...Continue Reading
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