Characteristics of Clone A1 LoxP parent cell line. (A) Clone A1 was grown in the absence of Dox for 3, 7, 14 or 18 days with daily media changes before GFP analysis by FACS. (B) Clone A1 was maintained for 60 days in the presence of Dox before removal 7 days prior to analysis of GFP expression. (C) Clone A1, Clone A12, or control 293 TETOFF cell genomic DNA, or pLoxPGFP plasmid DNA (+ve) was digested with EcoRI or KpnI and analysed by Southern blotting using a GFP gene probe. The positions to which DNA size markers migrated are indicated (kbp).