Unlinked structural genes for the developmentally regulated isozymes of sn‐glycerol‐3‐phosphate dehydrogenase in mice

Genetic variants that affect the heat stability and ionic charge of the adult isozyme of glycerol‐3‐phosphate dehydrogenase (EC 1.1.1.8) map to a gene, Gdc ‐ 1 , located on chromosome 15. A second isozyme of glycerol‐3‐phosphate dehydrogenase, structurally homologous to the product of the Gdc ‐1 locus and expressed predominantly in undifferentiated tissues, has previously been identified. We have now discovered an electrophoretic variant of this embryonic isozyme. This expression is determined by a codominant allele of the gene, Gdc ‐ 2 , that maps to the distal end of chromosome 9 as inferred from the observed gene order Mpi ‐ 1–d‐Mod‐1–Gdc‐2 .