Genome
size, a fundamental aspect of any organism, is subject to a variety of mutational and selection pressures. We investigated
Genome size evolution in haploid,
diploid, and tetraploid initially isogenic lines of the yeast Saccharomyces
cerevisiae. Over the course of ~1,800 generations of mitotic division, we observed
convergence toward diploid DNA content in all replicate lines. This convergence was observed in both unstressful and stressful environments, although the rate of convergence was dependent on initial ploidy and evolutionary environment. Comparative
genomic hybridization with microarrays revealed nearly euploid DNA content by the end of the
experiment. As the vegetative life cycle of S. cerevisiae is predominantly diploid, this experiment provides evidence that genome size evolution is constrained, with selection favouring the genomic content typical of the yeast''s evolutionary past.
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