Chromosomes that harbor dominant sex determination loci are predicted to erode over time—losing genes, accumulating transposable elements, degenerating into a functional wasteland and ultimately becoming extinct. The Drosophila melanogaster Y chromosome is fairly far along this path to oblivion. The few genes on largely heterochromatic Y chromosome are required for spermatocyte‐specific functions, but have no role in other tissues. Surprisingly, a recent paper shows that divergent Y chromosomes can substantially influence gene expression throughout the D. melanogaster genome.1 These results show (...) that variation on Y has an important influence on the deployment of the genome. BioEssays 30:409–411, 2008. © 2008 Wiley Periodicals, Inc. (shrink)