Fibroblasts were harvested from one T25 flask for karyotyping after 0–30 min in 0.02 μg/mL colcemid (KaryoMAX®; Gibco), depending on the culture, by selectively trypsinizing (0.05% Trypsin-EDTA; Gibco) to remove 1/3–1/2 of the cells. Cells were pelleted and resuspended in 5 mL of 0.0675 M potassium chloride and incubated at 37°C for 25 min. Cells were fixed in five parts methanol to one part acetic acid (5:1 fix) and washed thrice by centrifugation. Fixed cell suspension was dropped onto prepared slides in a humidified chamber (42%) at 27°C. Spreads were stained with Giemsa for 7 min and then imaged and karyotyped using the CytoVision System (Leica Biosystems). All fibroblast lines were karyotyped after initial banking and again after expansion for reprogramming, providing a standard for comparing the iPSCs.

iPSCs were harvested from one well of a 6-well plate after 30–60 min in 0.02 μg/mL colcemid using Accutase for feeder-free conditions or 0.05% trypsin-EDTA for feeder conditions and treated the same as the fibroblasts. Any contamination from the feeder layer was easily identifiable as mouse chromosomes instead of NWR and eliminated from the analysis.

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