Patterns in genome evolution

Among the recent advances that have furthered our understanding of genome evolution, some of the most important information has come from studies on the conservation of the mammalian X chromosome and the conservation of several linkage groups in divergent mammalian species. In addition, I believe that studies on gene duplication by tetraploidy in teleost fish provide evidence that the mammalian ancester underwent a round or two of tetraploid evolution, presumably at the stage of fish. It is possible that we might soon be able to deduce the genomic structure of the Devonian fish ancestor.