We have systematically searched the whole of the Y chromosome for transcription units and have discovered that the majority of genes are members of Y-amplified families expressed specifically in testes. The association of Y deletions with male infertility, and the abundance of testis-specific gene families, suggests that, over evolutionary time, the human Y chromosome may have acquired a specialized role in male germ cell development. With this hypothesis in mind, we are engaged in collaborative efforts to sequence the entire chromosome. We are also studying autosomal defects that cause severe spermatogenic failure in mice. In females, one X chromosome is silenced by X inactivation, a process often assumed to have evolved on a broadly regional or chromosomal basis.
Many extant genes appear to be intermediates.
Further, we suspect that, for each gene or cluster, X inactivation was an adaptation to decay of an homologous, Y-linked gene. Selected Publications Bohossian, H.B., Skaletsky, H., Page, D.C. Unexpectedly similar rates of nucleo-tide substitution found in male and female hominids. D.C. An azoospermic man with a de novo point mutation in the Y-chromosomal gene USP9Y. Nature Genet. D.C. Four evolutionary strata on the human X chromosome. Lahn, B.T., Page, D.C. Retroposition of autosomal mRNA yielded testis-specific gene family on human Y chromosome.