TSPY1 and gonadoblastoma: Page hypothesized the existence of a gene on the Y chromosome (the gonadoblastoma locus on the Y chromosome or GBY).9 More recently, it has been speculated that more than one gene may be implicated in gonadoblastoma, and it is also possible that some relevant genes are present in multiple copies.10 The main candidate for GBY is TSPY, a gene that has several homologous copies.