Sex determination and the Y chromosome: the application of molecular genetic technique to behavioral genetics.

In mammals, the Y chromosome mediates both gonadogenesis and spermatogenesis. It is also known to influence such traits as histocompatibility, sperm head morphology, pubertal (but not adult) testosterone level, sexual behavior, and aggressive behavior. An immediate goal in my laboratory is the isolation and characterization of the Y chromosomal gene responsible for initiating differentiation of the primitive bipotential gonads to become testes: the Y chromosomal gonadogenesis gene. Function of this gene initiates a cascade of events involving large numbers of other genes scattered throughout the genome, but it is not responsible for initiating development of all of the male phenotype; where : is XXSxr karyotype males, bearing the Sxr region of the Y chromosome which includes this gene, are sterile. It is not known if this gene influences those behaviors known to be influenced by the Y chromosome. If animals with an XXSxr karyotype, transgenic for specific Y chromosomal genes, could be produced, questions such as this could be answered. The developmental biology of the testis, molecular genetics of the Sxr region of the Y chromosome, and isolation of the testis determination gene from DNA of XXSxr males are discussed. Also discussed are the production of transgenic mice and the prospects for using such animals as coisogenic strains, differing by precisely known DNA sequences, in behavior genetic analysis. Such animals could be used both to test for behavioral phenotype and to dissect out biochemical and neurological mechanisms responsible for the behavior.