The origin of the duplicate genome in baker's yeast has been revealed: it arose when cells of two different species fused early in yeast's evolution.
Whole-genome duplication has happened during the evolution of many organisms, including yeast — in which researchers had thought it was a spontaneous event. Marina Marcet-Houben and Toni Gabaldón at the Centre for Genomic Regulation in Barcelona, Spain, analysed the genomes of Saccharomyces cerevisiae to reconstruct the evolutionary history of each of the yeast's genes. They concluded that each of the two subgenomes originated from a different lineage. Over time, there were extensive genomic rearrangements and gene loss.
This hybridization could have given yeast an advantage by bringing together different physiological properties.