(A) RNase protection assay of reticulocyte RNA, using the β⁶⁵⁴ riboprobe. Protected fragments of normal and aberrant transcripts are 129 bp and 189 bp, respectively. The lanes are represented by M: Marker (pBR322 DNA-Msp I); 1: Proband LI-1; 2: Proband LII-3; lanes 3 to 8 are the asymptomatic heterozygotes; N: normal; 9: CII-1 (β IVS 2-654 homozygote) and 10: AH (β IVS 2-654/(^Aγδβ)⁰ thalassemia). (B) RNase protection assay of RNA extracted from erythroblasts, cultured from CD34⁺ peripheral progenitors, using the β⁶⁵⁴ probe. Protected fragments of the normal (β^N) and aberrantly spliced (β⁶⁵⁴) transcripts, at 129 and 189 bp, are indicated. The lanes are represented by M, pBR322 DNA-Msp I; 1, RH (5 μg RNA); 2, RH (1 μg RNA); 3, normal control.