ENU-induced A to G transition at base pair 66,694,870 (v38) on chromosome 15, or base pair 24,117 in the GenBank genomic region NC_000081 encoding Tg. The mutation corresponds to residue 3,788 in the NM_009375 mRNA sequence in exon 5 of 48 total exons. The mutation results in a serine to glycine substitution of position 1,256 (S1256G) in the thyroglobulin protein.