The mutation is an A-to-G transition in the acceptor splice site of intron 14 (TATCAG->TATCGG) (position 24788 in Genbank genomic region NC_000081). cDNA sequencing detects no normal mature transcripts in homozygous mutant mice, but instead reveals two aberrant splice products. One, resulting from use of a cryptic acceptor splice site in exon 15, is missing 14 nucleotides from the 5' end of exon 15. The second abnormal splice product, generated using the acceptor splice site of intron 15, entirely lacks exon 15; its reading frame is shifted after codon 566, leading to a premature termination codon following codon 594. (J:134446)