Representation of the genomic and cDNA structure of the normal β allele (A) and the mutant β allele (B) showing the products obtained by RT-PCR using the primers AP1/AP2 and AP3/AP2. OP (5′-GTCTGTGTGTGCTGGCCCATCA-3′) is an oligonucleotide probe used to hybridize Southern-blotted cDNA fragments. Sequences of the primers are AP1: 5′-CTGAGGAGAAGTCTGCCGTT-3′, AP2: 5′-GCTTAGTGATACTTG TGGGCC-3′, and AP3: 5′-TGAGGAGAAGTCTCGCGTTAC-3′. A β⁶⁵⁴ riboprobe for detecting the normal and aberrantly spliced transcripts was generated by RT-PCR from a hemizygote for the β IVS 2-654 mutation, using primers AP4 (5′-CAATGTATCATGCCTCTTTGCAC-3′) and AP2.