Homologous insertion event in the Ercc1 locus. The targeted integration event was imprecise, containing a 1569bp deletion on one copy of the duplication (compared to the predicted product). This deletion begins at the RS(I-SceI) cut site and removes the 3' UTR of Ercc1 and all of Ciao1, ending 120bp upstream of the beginning of the HPS1 protein-coding region. The order around the targeted integration event is: SMC2, Ercc1 (wild-type), Ciao1 (wild-type), 5' portion of HPS1, FRT site, RS(I-CreI) site, w+mC, 5' portion of SMC2, Ercc1 (mutated copy), HPS1.