Structure of the teximY gene cluster in the sex-determining region of the Y chromosome of Xiphophorus maculatus . Red arrowheads show the position and predicted transcription orientation of teximY copies. The four sequenced BAC clones (B14, B29, B17 and N20) are shown as black lines. The distance between teximY copies is given. Locations of the Y-specific Y-cript pseudogene and of two copies of the type 4 melanocortin receptor gene mc4r are indicated.