SISTER CHROMATID EXCHANGES IN TRADESCANTIA-PALUDOSA

A modified fluorescence-plus-Giemsa technique is described that allows differential staining of sister chromatids in root tip cells from cuttings of T. paludosa. With this staining technique, chromatids with both DNA strands unsubstituted are differentiated from chromatids containing 5-bromouracil in place of thymine in 1 of the strands of the DNA duplex. The baseline level of sister chromatid exchanges was shown to be dependent on the concentration of 5-bromodeoxyuridine in the treatment solution, the mean frequency being 43.5 sister chromatid exchanges/cell for the experimental protocol suggested.