Fluorochrome banding

Different segments of the polytene chromosomes resulted in a differential banding after staining with a mixture of DAPI and propidiumiodid (DAPI/PI)(see figure).

Areas of euchromatin showed in dark blue, while centromeric and telomeric heterochromatin displayed a pink color. Especially striking were the white bands inside the pink colored cHC of some chromosomes. Their position corresponded to the strong DAPI bands. In this way the strong DAPI bands could not only distingished easily because of their greater brightness, but also because of their color, significantly different from the rest of the cHC.

Figure: Differential staining of polytene chromosomes of Phaseolus coccineus cv. Preisgewinner with a mixture of the fluorochromes DAPI and propidiumiodide under UV-excitation in filter set for DAPI fluorescence. Euchromatin is dark blue, heterochromatin is pink or white. Note that here one of the two chromosomes K is torn apart during the preparation (double arrow). The scale bar represents 10 µm.