FACS-sorted GFP⁺ cells from a C-GFP clone and mean frequency of GFP⁺ cells. (A) GFP⁺ cells were sorted and cultured for 1 wk to verify functional GFP expression (percentages are shown). (B) Mean numbers of GFP⁺ cells/10⁶ cells. Each open square indicates a clonal mean of 12 subclones for C-GFP; filled triangles show A-GFP. The blue line with closed squares and the red line with triangles show means of all C-GFP and A-GFP clones, respectively. The entire experiment was performed twice with similar results: once without selection of cells with a single-copy transgene (not depicted) and the second time in a more stringent comparison with all clones having only a single-copy transgene, as reported in this paper. FSC, forward scatter.