βh2 and βh3 are not expressed in any of the promoter-deletion embryos. (A) Schematic map of the D allele with the highly expressed β-like globin genes as dark bars and genes potentially expressed at low levels as white bars. (B) RT-PCR analysis of βh2 transcription in cDNA from e10.5 yolk sac. Lanes with genomic DNA (50 ng) are labeled G, marker lanes are labeled M, and genotypes of yolk sac samples are labeled. Expected sizes of PCR products from the βh2 cDNA and genomic DNA are marked. Genomic bands verify the ability to amplify the βh2 cDNA if it was present. (C) RT-PCR analysis of βh3 transcription in cDNA from e10.5 wild-type D/S (lanes 1-3), Δβh1/S (lanes 4, 5), ΔEy/S (lanes 6, 7), and ΔEyΔβh1/S (lanes 8, 9) yolk sac. G represents genomic DNA. PCR primers preferentially amplified cDNA from βh3 and, less efficiently, from Ey (2 mismatches on both primers). Uncut bands from any gene measured 96 bp. βh3 can be distinguished from Ey because the βh3 amplicon cut with NcoI to 64 bp but not with PvuII and the Ey amplicons cut with PvuII to 75 bp but not with NcoI.