SKY analysis suggests that mosaic aneuploidy is due to stochastic gain and loss of chromosomes.

Detailed karyotypes obtained from SKY analysis of H7, H9, and normal lymphocytes. Only numerical aneuploidies are shown, some of which included simultaneous chromosomal gains and losses. Forty chromosome spreads were analyzed for each cell type. There is no statistically significant trend in individual chromosome loss or gain. Individual chromosomes were lost and/or gained at rates of 0–4%, consistent with rates obtained from chromosome counts and FISH analysis.