CYTOLOGIA
Online ISSN : 1348-7019
Print ISSN : 0011-4545
Ultrastructural Analysis of Radiation Induced Chromosome Breaks and Rearrangements
J. L. FernándezA. CamposD. CajigalV. J. Goyanes
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1990 年 55 巻 4 号 p. 595-600

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Chinese Hamster chromosomes R-banded in vitro were gamma-irradiated and chromatid breaks and rearrangements examined by electron microscopy employing whole-mounting tech nique. Breaks were preferentially located at the point of transition between G- and R-bands where the chromosome showed an average diameter 71.65% of the wide condensed R-bands. This result was similar to the average diameter of narrow G-bands. Three chromosomes which were thin sectioned presented their broken terminal end organized as a coil constituted by two 23 nm wide chromatin fibers coiling together. Coils diameter was 43.70% of the mean chromatid diameter. The border of damage-breakage was analyzed in whole-mounted chromosomes where breaks were photoinduced in BrdU-substituted DNA. Measurements of the angle of the sharp border of damage with respect to the chromatid axis showed a tendency to be more perpendicular as condensation progressed. These results clearly correlate with the several levels of chromatin fiber organization of the metaphase chromosome.

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© The Japan Mendel Society
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