A neomycin resistance gene with a polyadenylation signal, but having a single loxP site in place of a promoter (loxP-neo-pA), resides 2.6 kb upstream of (distal to) and in the same transcriptional orientation as the insulin 2 gene on Chromosome (Chr) 7, between the domain of influence of Chr 7 imprinting center (IC) 1 (H19 DMR) and that of IC2 (KvDMR1). (J:130399)