The effect of cell proliferation on instability index. (A) STHdhQ 111/+cells were maintained at the restrictive temperature (39°C) (no cell division) for 9 weeks without subculture (red), and control cultures at the permissive temperature (33°C) (actively dividing) were subcultured every week (blue). GeneMapper traces of genomic DNA isolated at 9 weeks are shown. (B) For the time-course study, cultures grown at 39°C and at 33°C were harvested at 0, 3, 5, 7 and 9 weeks, and genomic DNA was analyzed to calculate the instability index. Representative GeneMapper traces and instability indices are shown from three independent experiments.