A new genetic variation of the malate dehydrogenase-like enzyme (MDL-1) in inbred rats and its possible linkage.

A new polymorphism in the mitochondrial fraction of kidney homogenates was found by using discontinuous polyacrylamide gel electrophoresis. The polymorphism is tentatively designated MDL-1, since the enzyme was visualized with the staining solution for NADP-malate dehydrogenase (MOD) but differs from MOD. MDL-1 expresses three phenotypes: MDL-1A (fast), MDL-1AB (intermediate), and MDL-1B (slow). Progeny testing from genetic crosses indicates that its expression is determined by two codominant alleles, Mdl-1a and Mdl-1b, which segregate in a simple Mendelian fashion. Preliminary linkage data suggest that the locus for MDL-1 is probably linked to the nonagouti-agouti locus in rat linkage group IV.