BAC recombineerting was used to generate a construct with a codon-improved cre recombinase sequence inserted into the translation initiation site in exon 2 of the glucagon (Gcg) gene, followed by n adenylation signal sequence. The large first intron of Gcg was replaced with a 300 bp synthetic intron to reduce the size of the final transgene construct that was injected into pronuclei of C57BL/6 zygotes. Founders were screened by PCR for transgene intregration, with 20 and 23 testing positive for integration. Line 23 was chosen for further analysis. (J:203933)