**Figure 3.** **Structural and numerical chromosome aberrations.** A total of 40 metaphases prepared from two independent cultures were evaluated by G-banding. For a given mitosis, all chromosome aberrations observed therein were listed. (**A**) Examples of structural (1a, b) and numerical (2) chromosome aberrations listed during scoring. (**B**) Frequency of all aberrations evaluated as the percentage of cells (mitoses) positive for one or more aberrations plotted over calendar age of the donors. (**C**) Number of individual aberrations within an altered mitosis plotted over calendar age of the donors. (**D**) Frequency of structural aberrations plotted over donor age. (**E**) Frequency of numerical aberrations plotted over donor age. (**B-E**) Mean values obtained for each donor; SEM < 20% of the values omitted for the sake of clarity; results of linear regression are stated as R^{2}: Pearson's coefficient for goodness of fit, p: probability for slope = 0, dotted lines: 95% confidence limits of linear regression, and *N.S*.: linear regression of the data revealed no significant age-related change in the parameters.