The study is by postdoctoral fellow and lead author Manolis Kellis of the Broad (rhymes with "code") Institute; Eric S. Lander, Broad director; and Bruce W. Birren, co-director of the Broad's sequencing and analysis program. It will be published online by Nature on March 7.
Scientists have postulated that in a handful of instances in evolutionary history, cells may have replicated their entire genomes in events called whole genome duplication, but no definitive proof existed. The Broad Institute work shows conclusively for the first time that the well-studied organism baker's yeast originated through this little-understood phenomenon, resolving a long-standing controversy on the ancestry of the yeast genome.
Whole genome duplication (WGD) may have occurred when a cell replicated its DNA normally, as it does every time it divides, but did not split it between two resulting cells, or two cells may have fused. The result is that a yeast cell with around 5,700 genes suddenly had more than 11,000. In this scenario, while one copy of the gene performs its designated function, the other is free to perform a new and potentially valuable use. In addition, the organism is able to evolve more rapidly with natural selection acting on thousands of duplicated genes simultaneously, allowing for large-scale adaptation to new environments.
This super-organism doesn't come without drawbacks. The excess genes cause instability in the genome and are deleted through mutation, gene loss and genomic rearrangement. As a result, millennia after the event, very few duplicated genes remain.
"This is the firs
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Massachusetts Institute of Technology