A G-to-A substitution in the 3' end of intron 2 in splice acceptor site CAG-GT effectively eliminating it but at the same time creating a new acceptor that moves the splice junction one base downstream (AAG-T) into exon 3. The resulting mRNA lacks the single G nucleotide from the start of exon 3 (part of codon 49), causing a frameshift and premature termination of the encoded protein.