Practice question

Drosophila sex hierarchy consists of master regulator Sex-lethal, intermediate regulators transformer and transformer-2, and terminal effectors doublesex and fruitless producing sex-specific isoforms via alternative splicing. Numerator X-linked genes activate Sxl in XX; Sxl directs female tra splicing; Tra with constitutive Tra2 directs female dsx and fru splicing. Genes Sox9, Sry, Fgf9 are mammalian male determinants operating via transcriptional activation and β-catenin antagonism; Wnt4/Rspo1 are mammalian ovarian regulators; Wt1, Lhx9, Gata4 are mammalian bipotential gonad factors. Thus canonical fly genes are Sxl, tra, dsx.