The Differences in Recombination Rate between the Male and Female in Rana nigromaculata and Rana brevipoda
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The linkages among six enzyme loci, SORDH, MPI, ENO, HK, Pep-B and LDH-B, situated on chromosome No. 4 were analyzed in order to examine the differences in recombination rates between males and females. Mating experiments were conducted by using heterozygous females or males of Rana brevipoda and Rana nigromaculata, heterozygous females of interspecific hybrids between R. nigromaculata and R. brevipoda and those between Rana plancyi chosenica and R. nigromaculata. The recombination rates among the loci controlling six enzymes located on chromosome No. 4 were found to be large in females when the frogs were pure species, while they became smaller when the frogs were hybrids. The recombination rates were almost zero in males in contrast to females. They had no relation to the existence of the sex-determining genes on the chromosomes of the species used in the present study. The differences in the recombination rates seemed to be attributable to that in the number of chiasmata. When the number of chiasmata became smaller, the recombination rates also became smaller, and in male frogs they seemed to approach zero. Thus, the present study showed that it may be better to use heterozygous males for the purpose of assuming the kinds of genes on specific chromosome. However, it may be better to use heterozygous females in order to clarify the mutual positions of loci on the same chromosome.
Scientific report of the Laboratory for Amphibian Biology
Institute for Amphibian Biology, Hiroshima University