Translocation Frequencies for X and Y Chromosomes Predicted by Computer Simulations of Nuclear Structure

For an improved understanding of the correlation between the formation of chromosome aberrations induced e.g., by ionising radiation, and the three dimensional structure of the genome, computer simulations of the human cell nucleus were applied to calculate relative translocation rates (Kreth et al., 1998). In the present study an extended computer model was applied taking into account the observed different morphology of both X chromosomes in human female cell nuclei. In the modelling of nuclear genome structure, “tensegrity forces” were introduced which allowed the simulation of different compartmentalisations of a chromosome territory. With the simulation of the observed surface ratio Aenv(Xa)/Aenv(Xi) ~ 1.4 (Aenv -enveloping surface) between the two X chromosome territories, marked differences in the translocation rates of both territories were predicted. These computer simulations show that the morphology of a given chromosome territory may have a profound influence on its aberration frequency allowing to establish a quantitatively testable correlation between these observables.