5 Aug 2011
Yitzhak (Tzachi) Pilpel
Weizmann Institute of Science, Israel
During evolution genomes are dynamically changing to present solutions to challenges in the environment. Individuals in a population compete on rapidly converging upon fit genomic solutions that are sequentially refined in steps, especially in the case of a-sexually reproducing species. In my talk I will ask how genomes of microbial species evolve not only by changing their DNA sequence but also by introducing large-scale changes in the structure of their genomes. In this seminar I will present our recent lab evolution experiment in which yeast evolved through months of well-defined and controlled environmental challenges, followed by monitoring of their genome dynamics. Surprisingly, the generation of several specific aneuploidies — the abnormal copy number of certain chromosomes — appear as a genome evolution operation that is extensively exercised by the species. These massive changes are rapidly discovered by cells and they serve as evolutionary "stepping stones" that later give way to more refined solutions that take longer to be converged upon. The study demonstrates how well controlled lab evolutionary experiments can advance our understanding of some basic mechanisms of evolution. This is joint work with Avihu Yona and Orna Dahan.