Assignment of the gene for NADH diaphoraseDia-1 to mouse chromosome 15

We have examined 14 Chinese hamster x mouse somatic cell hybrids segregating mouse chromosomes for the expression of NADH-dependent diaphorase (Dia-1, cytochrome b₅reductase, EC 1.6.2.2). Isoelectric focusing allowed the discrimination of mouse Dia-1 isozymes from those of the Chinese hamster in the hybrids. Correlation of the loss or retention of individual mouse chromosomes with expression of mouse diaphorase isozymes resulted in the assignment of the gene for Dia-1 to chromosome 15. Dia-1is the first biochemical gene that can be detected in cultured cells assigned to this chromosome and will therefore provide a convenient marker for future somatic cell genetic studies.