How Soon After Irradiation Do Chromosome Aberrations Form and Become Irreversible: a Direct Analysis by Means of the Premature Chromosome Condensation Technique
Radiation-induced chromosome breaks and rearrangements may play a crucial role in both mutagenesis and carcinogenesis. Yet, because radiation induces far more initial chromosome breaks than are observed as aberrations at metaphase, it has not been possible to examine the kinetics of primary breakage and rejoining in lymphocytes. A simple method for cell fusion and premature condensation induction is used to study primary chromosome breakage, rejoining and formation of irreversible chromosome rearrangements (e. g., rings, dicentrics) in G0 human lymphocytes. The dose-response relations for chromosome fragments analyzed immediately or 1, 2 or 24 h after exposure were found to be linear. Chromosome fragment rejoining and ring formation were completed about 6 h after irradiation. with the use of C-banded chromosome preparations, it could be seen that dicentric chromosomes were also formed in the G0 lymphocytes during the chromosome fragment rejoining process. Regardless of dose and post-irradiation time, rings were found to follow a Poisson distribution, whereas chromosome fragments were overdispersed.
KeywordsChromosome Aberration Ring Formation Chromosome Fragment Human Peripheral Blood Lymphocyte Dicentric Chromosome
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