Mapping of DNaseI HSs in the HS-62.5 and 3′HS1 regions of WT and ΔHS-62.5, Δ3′HS1 mice. DNaseI series from WT and homozygous mutant mice were digested with EcoRV and hybridized with probes to the 3′ end of each restriction fragment. After hybridization to HS-62.5 or 3′HS1 region probes, blots from mutant mice were stripped and rehybridized to a probe to the 5′HS4 region to demonstrate the quality of the DNase series. The edge of a 1-kb marker lane is observed on the far left. DNaseI digestion increases from left to right. The characteristic doublet of HSs for the HS-62.5 and 3′HS1 regions in WT samples are marked by arrows (left blots). The characteristic doublet of 5′HS4 is marked by arrows (right blots). An asterisk marks the size of expected fragments if a HS formed at the site of the targeted deletions in mutant samples (middle blots). Left blots are from WT mice. Middle and right blots are from homozygous ΔHS-62.5, Δ3′HS1 mice. Probes used are indicated above each panel.