ENU-induced A to G transition at base pair 66,674,050 (v38) on chromosome 15, or base pair 3,297 in the GenBank genomic region NC_000081 encoding Tg. The mutation corresponds to residue 642 in the NM_009375 mRNA sequence in exon 5 of 48 total exons. The mutation results in an aspartic acid to glycine substitution of position 207 (D207G) in the thyroglobulin protein.