The mutation is an A to T transversion at position 25,262,891 of the C57BL/6J mouse genomic DNA sequence for Chr 12 (NCBI Genbank Build 37.1), within exon 3 (exons 1-3 are not included in the Genbank annotation of the genomic DNA sequence of Grhl1, region NC_000078). Normally, two isoforms of the protein are expressed due to alternative mRNA splicing. The mutation in this allele corresponds to nucleotide 366 of the mRNA sequence for isoform 1; it converts the triplet encoding arginine at codon 72 to a termination codon (R72Ter). As the mutation is in exon 3, which is absent from isoform 2, it is predicted not to affect isoform 2.