The male sex-determining region of medaka and its position on the sex chromosome. (A) The BAC clones covering the sex-determining region of medaka were isolated by screening using dmrt1bY as the probe. The contig was extended by screening the BAC library with BAC end markers in both directions. Mn0168M02 (0168), Mn0209O12 (0209), and Mn0113N21 (0113) on the Y chromosome, as well as Mn0195H08 (0195) from the X chromosome were used for further analysis. The dmrt1bY gene (gray box) is located on clone Mn0113N21. The Olaflnk genes (white boxes) are located on Mn0113N21, Mn0168M02, and Mn0195H08. The gray circles indicate the markers that were derived from BAC end sequences of Mn0168M02 or Mn0113N21, present in Mn0195H08. The dotted line in Mn0195H08 indicates that this region does not exist in this clone, but the flanking regions are present. (B,C) The linkage map close to dmrt1bY. The sex-determining region is located on the long arm of the sex chromosome (LG1). All markers shown in the diagram except for dmrt1bY are present on both the X and Y chromosomes (B). Markers casp6 (caspase 6) and casp3B (caspase 3B) were used to screen the HNI BAC library and Mn0019I23 (0019), Mn0036H11 (0036), Mn0065F06 (0065) and Mn0046N20 (0046) were isolated (not drawn to scale) (C). End-sequencing of these clones revealed the existence of other genes (marked by triangles). Numbers indicate distances in centimorgans in sex-reversed XY female meiosis.
