The Y chromosome.

The Y chromosome has evolved to provide sex determination in mammals. In association with its evolution, genes important for spermatogenesis have been sequestered on this chromosome. Further, X chromosome inactivation has developed as a mechanism to prevent over-expression of genetic factors important for somatic function in females, with maintenance of their activity in males. The multi-repeat organization of the Y chromosome and limited regions of crossover with other chromosomes predisposes it to internal recombination and loss of genes that may be important for spermatogenesis. Y chromosome microdeletion testing of infertile men with non-obstructive azoospermia provides prognostic information useful for management of these patients. In the presence of a complete deletion of the azoospermic factor a (AZFa) or AZFb regions, sperm retrieval is highly unlikely. Recent advances in our understanding of the organization and function of the Y chromosome are likely to enhance further the role of the Y chromosome in normal spermatogenesis and fertility.