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[Torsional tension in metaphase chromosome DNA]
A D Gruzdev1, F E Kuzin, E R Galieva
1Institute of Cytology and Genetics, Siberian Division, Russian Academy of Sciences, Novosibirsk, Russia.
Abstract:
The torsional tension in DNA of isolated metaphase chromosomes from murine fibroblasts was measured by the microfluorescent method. The method is based on the ability of a fluorescent dye ethidium bromide to compensate for the negative torsional tension in topologically closed DNA by intercalation between DNA base pairs. The value of the relative twist difference delta Tw/Tw = -0.1 was found in a bulk (about 3/4) of unconstrained chromosomal DNA. In interphase nuclei, the torsionally stressed DNA comprises about 15%, with value of delta Tw/Tw = -0.075. We suppose that the tension in chromosomal DNA was created in the prophase stage of mitosis by condensines, the drivers of chromosomal condensation.