Gaussian-chain model for the formation of chromosome aberrations

In this report a model is developed for the formation of chromosome aberrations by approximating interphase chromosomes as random-walk Gaussian chains. The following results support the model: (1) The ratio of dicentrics to centric rings (F) was calculated for the case of equal-sized metacentric chromosomes in a spherical nucleus: F = 4-23, which agrees well with the experimental range of 5-20 reported in the literature for human lymphocytes. (2) The prediction of the model that the probabilities for intrachromosomal and interchromosomal exchanges are inversely proportional to nuclear volume agrees well with data for chromosome exchanges in lymphocytes compared to normal fibroblasts, and with data for survival of plateau-phase Chinese hamster V79 cells after postirradiation treatment with hypertonic salt solutions. (3) The prediction of the model that the probability of interchromosomal exchanges is greater in spherical nuclei than in flat nuclei agrees with experimental data for differences in survival of human fibroblasts (ataxia telangiectasia and normal) irradiated as monolayers and plated immediately or several hours (delayed plating) after irradiation.