α-globin/MPO gene construct. Genomic MPO region between exon 9 and exon 10 from MP and a normal subject cloned into exon 3 of α-globin gene in vector pSVEDα1W (BstEII, cloning site). □, α-globin exons; ▪, MPO genes. Continuous lines, introns. Δ14, site of the 14-base deletion in α1/MPO-Δ14 construct. 1, observed normal splicing. 2, expected splicing. GT, alternative donor splice-site. gt and ag, normal splicing sites.