Percentage of GFP⁺ cells from C-GFP and A-GFP clones. 60 subclones each from C-GFP and A-GFP lines were monitored for GFP⁺ cells by flow cytometry every week for 6 wk. Green boxes are subclones with numbers of GFP⁺ cells ≥0.01% or 100 GFP⁺ cells/10⁶ cells. Bolded borders indicate subclones that were sorted for GFP⁺ cells; red (black) borders indicate sorted subclones that did (did not) expand or survive for subsequent analyses.