PROGRESS REPORT ON THE LINKAGE GROUPS OF MEDAKA (Oryzias latipes)

¹ Department of Integrated Biosciences, Graduate School of Frontier Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan

² Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan

³ Laboratory of Developmental Gene Regulation, Brain Science Institutes, RIKEN, Wako-shi, Saitama 351-0198, Japan.

⁴ Division of Biological Sciences, Graduate School of Science., Hokkaido University , Sapporo 060-0810, Japan

⁵ Department of Fisheries, Faculty of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-01, Japan

⁶ National Research Institute of Aquaculture, Hiruta, Tamaki, Mie 519-0423, Japan

⁷ Department of Biology, Ochanomizu University, Bunkyo-ku, Tokyo 112-8610, Japan

For a teleost fish Medaka Oryzias latipes, we recently mapped 633 markers (488 AFLPs, 28RAPDs, 34 IRSs, 75 ESTs, 4 STSs and 4 phenotypic markers) into 24 linkage groups, corresponding to the haploid chromosome number. Linkage was determined using a reference typing DNA panel from 39 cell lines established from 39 backcross progeny obtained by crossing AA2 female and (AA2 female x HNI male) F1 male. The total map length of 1354.5 cM and the haploid genome size of 800 Mb give a value of 1354.5 cM/800 Mb for the male meiosis. Thirteen to 49 markers for each linkage group were obtained. Conserved syntheny between Medaka and zebrafish was observed for two independent linkage groups. Unlike zebrafish, however, the Medaka linkage map showed obvious restriction of recombination in the linkage group containing the male-determining region (Y) locus compared to the remaining linkage groups.