Instability of chromosomal abnormalities has been well documented in vivo and in vitro. Among practicing clinical geneticists, it is widely understood that mar elements are unstable and likely to present as mosaic in vivo (Liehr et al., 2010). Similarly, trisomies found early in pregnancy during chorionic villus studies may undergo “trisomy-to-disomy” rescue via uniparental disomy (Spence et al., 1988). Moreover, high rates of aneuploidy in source cells do not always translate into similarly high rates in the derived hiPSCs, likely because aneuploidies may be subjected to selective pressures during reprogramming, resulting in different levels of tolerance in the reprogramming cells (Hamada et al., 2012).
