Journal article

Sex determination in platypus and echidna: autosomal location of SOX3 confirms the absence of SRY from monotremes

MC Wallis, PD Waters, ML Delbridge, PJ Kirby, AJ Pask, F Grutzner, W Rens, MA Ferguson-Smith, JAM Graves



In eutherian ('placental') mammals, sex is determined by the presence or absence of the Y chromosome-borne gene SRY, which triggers testis determination. Marsupials also have a Y-borne SRY gene, implying that this mechanism is ancestral to therians, the SRY gene having diverged from its X-borne homologue SOX3 at least 180 million years ago. The rare exceptions have clearly lost and replaced the SRY mechanism recently. Other vertebrate classes have a variety of sex-determining mechanisms, but none shares the therian SRY-driven XX female:XY male system. In monotreme mammals (platypus and echidna), which branched from the therian lineage 210 million years ago, no orthologue of SRY has been foun..

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University of Melbourne Researchers