Expression of β-like globin genes in ▵5,6 ▵H/WT heterozygous mice. The Hbb^D allele (D) carries the targeted mutation, whereas the Hbb^S allele (S) is wild-type. RNA was analyzed from dpc 10.5 yolk sac, dpc 15.5 fetal liver, and adult peripheral blood using RT-PCR assays for Ey, bh1, and adult primers (top, middle, and bottom panels). WT, wildtype D/S animals; ▵5,6, mutant ▵5,6 ▵H/S heterozygous mice. S and D mark the RT-PCR products from the S and D alleles, respectively.