Linkage relationships of gene loci in the Medaka, Oryzias latipes (Pisces: Oryziatidae), determined by backcrosses and gynogenesis

Abstract

Linkage relationships of 11 enzyme loci and 2 visible mutant loci were investigated in the Medaka, Oryzias latipes, using backcrosses and gynogenesis. Results of four crosses for three loci were not in agreement with the Mendelian expectation of a 1 homozygote:1 heterozygote segregation ratio. Some locus pairs showed a significant excess of parental types at the 5% confidence limit. At the 1% confidence limit, however, results of all locus pairs analyzed showed nonsignificance. The results of sex-linked locus tests showed that no loci were sex linked at the 1% confidence limit. Under complete interference conditions, gene-centromere distances (cM) were as follows: Me, 2.6; Adh, 10; Sod, 17; Sdh, 18; Pgm, 31; Ck-A, 31; Gpdh, 32; Pgd, 45; Amy, 47; and Ldh-A, 50. High heterozygous fractions observed for Pgd, Amy, and Ldh-A suggest that exactly one crossover happened between these genes and their centromeres and that strong interference exists in chromosomes carrying these loci.