ENU-induced T to C transition at base pair 3,159,475 (v38) on chromosome 8, or base pair 120,175 in the GenBank genomic region NC_000074 encoding Insr. The mutation corresponds to residue 4,096 in the mRNA sequence NM_010568 within exon 19 of 21 total exons. The mutation results in a phenylalanine to leucine substitution at position 1,203 (F1203L) in the INSR protein.