ENU-induced T to A transversion at base pair 50,951,506 (v38) on chromosome 14, or base pair 7,204 in the GenBank genomic region NC_000080 encoding Pnp. The mutation corresponds to residue 1,035 in the mRNA sequence NM_013632 within exon 5 of 6 total exons. The mutation results in substitution of leucine 252 for a premature stop codon (L252*) in the PNP protein.