ENU mutagenesis induced a T to A transversion at position 34148572 (Genbank genomic region NC_000077). The mutation is located within the donor splice site of intron 21 from the ATG exon, two nucleotides from the previous exon. (J:173592) Additional incidental mutations were detected in sequencing for the causative mutation, Dock2m1Btlr, and may be present in stocks carrying this mutation.