A diagram and RT-PCR results showing aberrant splicing of the human βIVS-2-654 transcript in theHbb^th-4/Hbb⁺ thalassemic mice. (A) The diagram shows the human βIVS-2-654 gene with aberrantly spliced β globin mRNA produced from the mutant gene compared with the correctly spliced β globin mRNA that would have been produced from a wild-type gene. The thick line between nucleotides 580 and 652 shows the region of IVS-2 that is maintained in the βIVS-2-654 mRNA. RT-PCR primers i and ii are shown at the location and in the direction in which they anneal to the RNA. Primer i anneals to sequences within the second exon of human β globin, and primer ii anneals to sequences within the third exon of human β globin. (B) An autoradiograph of polyacrylamide gel electrophoresis of RT-PCR with primers i and ii on RNA from a heterozygous huβ ^s/Hbb⁺mouse (lane 1), a heterozygousHbb^th-4/Hbb⁺ thalassemic mouse (lane 2), a HeLa cell line transfected with a βIVS-2-654 gene (lane 3), and a normal human (lane 4) is shown. Aberrantly spliced β globin mRNA and correctly spliced β globin mRNA RT-PCR products are 303 bp and 230 bp, as labeled.