Map of mutant D alleles generated by homologous recombination. (A) Map of the mouse β-globin locus. Arrowheads represent genes. Vertical arrows represent HSs. ORG indicates olfactory receptor gene. The extent of the DNaseI-sensitive domain is diagrammed below the locus map. (B) Diagrammatic representations of the targeted deletions generated. Striped region designates the UHR, the region upstream of the LCR that has homology to the region deleted in the Hispanic deletion.