Genomic structure of the GPHe(GL) allele and nucleotide sequences of exon-intron junctions. (A) Strategy for genomic amplification of exons and their flanking sequences. Four segments with each covering a unique exon were amplified from either the 9.2- or 4.3-kb Msp I fragment. Segment e, which overlaps a and b, was amplified from total genomic DNA using the He-specific primer P2 and the reverse primer for the b segment (see Materials and Methods). As shown, the GPHe gene from GL also is a GPB-A-B hybrid in the exon II-intron 2 junction region.12 (B) Exon-intron junction structures and splice site scores for the determined acceptor and donor splice sites (overlined). Exon sequences are in capital letters and their encoded amino acid residues are shown. Dots denote omission. Two point mutations, a g→t transversion in the 5′ donor gt element of exon III and a t→g transversion at −6 position near the exon IV acceptor site, are indicated by arrows. The newly created acceptor splice site in exon V and its score are also shown. The consensus sequences of the 3′ acceptor and 5′ donor splice sites are listed at the bottom.