A BAC (RP23-340E18) containing the Gck locus was modified by inserting cre recombinase with a nuclear localization sequence and a polyA at the ATG site in exon 1 of Gck by homologous recombination in bacterial cells. The purified construct was injected into C57BL/6 pronuclei to generate founders. Line numbers are not available. (J:206002)