Detection of a null allele for MDH isozymes in the guppy (Poecilia reticulata), with special reference to sex-linked inheritance.

Malate dehydrogenase (MDH) was examined by starch gel electrophoresis for strain differences in the guppy, Poecilia reticulata. The electrophoretic patterns revealed duplicate gene loci encoding a mitochondrial form of MDH and the existence of a null allele at one of the duplicate loci. Different phenotypic frequencies at Mdh-4 were observed among 9 strains and between males and females within each strain. The progeny tests for Mdh-4 variants in the inter-strain crosses indicated a mode of partial sex-linked inheritance.