DNA lysis is involved in the simplified fluorescence plus Giemsa method for differential staining of sister chromatids

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Abstract
The DNA labelling of the bifilarly 5-bromodeoxyuridine- to-substituted chromatid decreased relative to that of the unifilarly substituted chromatid with increasing duration of HB pretreatment (Hoechst 33258 plus black light at 55° C). Sister chromatid differential staining was detected by Giemsa as well as a DNA-specific dye, ethidium bromide, after 4 s of HB pretreatment. The contrast of sister chromatid differential staining was improved with increased duration of HB pretreatment or by incubation with exonucleases. Hydrogen donors such as cysteamine, cysteine, and L-ascorbic acid inhibited the HB pretreatment, but this inhibition could be overcome by increasing the duration of HB pretreatment.