Fig. 3. Generation of a conditional cell-ablation mouse by gene targeting. (A) The DTA176 coding sequence is targeted into the Rosa26 locus, and is not expressed until the transcription stop is removed by Cre-mediated recombination. (B) Southern blot screen for ES cells and PCR genotyping for animals. EcoRV digestion and a 5' external probe were used to identify targeted ES cells, which have a 4.1 kb band in addition to the wild-type 11.5 kb band.