A pronounced sex difference when two linked loci of the Japanese brown frog Rana japonica are recombined.

To investigate the sex differences of crossing-over in Rana japonica, the recombination frequencies between two linked loci, LDH-B and MPI, were examined in offspring obtained from 29 matings involving either females or males heterozygous at both loci. No recombinants were found among 303 offspring bred from 6 heterozygous males, whereas 160 were parental and 138 were recombinants among 298 offspring bred from 9 heterozygous females. The recombination frequency was 46.3%. These results show that the sex difference when two loci were recombined was marked and significant in Rana japonica.