The current dogma describing the genetic control of development assumes a hierarchy of regulatory genes. In the simplest case, a master control gene directly regulates secondary genes which, in turn, regulate the expression of other genes. In principle the master control genes can be recognized by the pleiotrophic effects caused by mutation, however, complex phenotypic changes are also associated with mutations in many nonregulatory genes. The bestdescribed examples of control genes are from relatively simple organisms with well-developed genetics, for example Drosophila and Caenorhabdltis. Unfortunately, identification of developmental control genes in mammals has proved to be difficult, presumably because homeotic and similar mutations are lethal. There is, however, one well-defined developmental control gene in mammals: TDF or the testis-determining gene (the same locus is called Tdy in mouse). Molecular cloning of TDF will not only facilitate exploration of the fundamental questions of sex determination, but should also provide a model for genetic control of development.
Regulation of CATSPER1 expression by the testis-determining gene SRY
