Detection of still more ancient whole-genome duplications previously has relied on direct observation of genomes that have been completely sequenced. Arabidopsis, for example, the first plant whose genome was entirely sequenced, was shown to harbor many small blocks of related genes in identical order along the chromosome--the telltale remnants of a whole-genome duplication. In Arabidopsis and other cases, however, the signs of whole-genome duplication are few and far between: most of the duplicate genes are quickly lost, leaving few obvious traces.
Whole-genome duplications have attracted attention as a possible mechanism to drive sudden bursts of evolution, like the one that so vexed Darwin over a century ago. While the vast majority of duplicate genes quickly accumulate mutations and are deleted from the genome, a few mutations will be selected for evolutionarily advantageous function. Rather than gradually collecting genetic novelty by single-gene duplications, simultaneously having a full genome's worth of raw material to elaborate new genetic function could drive sudden evolution. But because of the rapid, massive gene loss after a whole-genome duplication, these events are notoriously difficult to detect after millions of years. So dePamphilis and colleagues relied on a statistical filter to hunt for ancient duplications.
In order to show that such an event occurred early in angiosperm history, dePamphilis and his colleagues had to compare the genomes of "basal" angiosperms--those whose an
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Source:Penn State