Figure 1.

Conditional targeting of the H19 locus. (A) The structures of the wild-type, targeted, and excised H19 loci are shown along with diagnostic restriction fragments. The solid arrowheads represent the loxP sites, the solid lines represent DNA contained within the targeting construct, and the dashed lines represent DNA outside the targeting construct. The two probes used for Southern analysis of ES cell clones and mouse DNA are shown and are located outside of the region contained within the targeting construct. Restriction sites are abbreviated as EcoRI (R) and KpnI (K). (B) KpnI-digested ES cell and mouse genomic DNA was hybridized to the 5′ probe, which detects a 7-kb fragment in wild-type (WT) H19 alleles, a 9-kb fragment in the floxed (H19loxP) allele, and a 4-kb fragment in the deletion allele (loxΔH19).