Genetic Analysis and Histology of Hypoplastic Kidneys in the Male Hypogonadic Mutant (hgn/hgn) Rat

Abstract Bilateral hypoplastic kidneys have been found to associate with the male hypogonadism rat (hgn/hgn). The hypoplastic kidney was persistent to the male homozygote for hgn and it was also seen in some females with unknown genotype. The affected kidney was apparently smaller in size than phenotypically normal one. When females with hypoplastic kidney were mated to proven heterozygous males for hypogonadism (hgn/+), the ratio of the affected testis to phenotypically normal one was 32: 20 in the Fl generation. This segregation ratio did not deviate siginificantly from the 1: 1 ratio expected from the hypothesis that the genotype of females with hypoplastic kidney in parent generation for hypogonadism would consist of hgn/hgn alone. The ratio expected from the other hypotheses was denied statistically. The ratio of the affected kidney to phenotypically normal one in both sexs of the Fi was 53: 50, fitting to 1: 1 hypothesis for a single autosomal recessive trait. There was neither a case showing the phenotypically normal kidney with the affected testis, nor the hypoplastic kidney with the phenotypically normal testis. The results suggest that the gene responsible for the hypoplastic kidney and the gene for hypogonadism would be identical or both genes reside in the close vicinity in a chromosome. The results also suggest that the homozygotes for hgn can be selected by the presence of hypoplastic kidney.