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

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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; andLdh-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.