Conservation, relocation and duplication in genome evolution

The advent of whole-genome sequencing and genome-wide transcriptional profiling has opened up new approaches to the resolution of questions that only a few years ago seemed unanswerable. At the same time they have revealed new and sometimes unexpected patterns of gene conservation and functional compensation, chromosomal clustering of transcriptionally related genes, relocation of genes to depopulate or overpopulate the X chromosome with certain functional classes of genes, and gene duplication and functional divergence. What makes molecular evolutionary genomics different from previous approaches is the generality of the results. Choice of genes, and the uncertainties of extrapolating from a sample of genes to the entire genome, is supplanted by direct genome-wide observations. In this article we examine some key recent experiments in RNA interference that illustrate some of the strengths and limitations of evolutionary genomic analysis.