Spontaneous chromosome abnormalities in Artemis defective cells. A. Chromosome breaks. B. Telomeric fusions. C. Example of a telomeric fusion in a CJ179 cell: sister chromatid union. Error bars represent standard deviation (SD). Frequencies of abnormalities per cell were calculated from three separate experiments. The total number of metaphase cells analysed were: GM08399 - 111, CJ179 - 193 and F01-240 - 174.