Tuesday, August 26, 2008

abstract to my seminar ppt...

Darwinian Evolution on a Chip

Brian M. Paegal, Gerald F. Joyce

PLoS Biol 6(4):e85. doi:10.1371/journal.pbio.0060085-


Darwinian evolution in nature has led to development of many sophisticated enzymes. Recapitulation of Darwinian evolution in vitro has emerged as chemical tool for optimizing functional ribozymes in the lab. A ribozyme that catalyzes template-directed ligation of oligonucleotide substrate was made to evolve continuously under the selective pressure of reducing substrate concentration. A micro-chip based automated serial dilution circuit was developed which carried out serial 10-fold dilution after exponential growth phase, this was repeated for 500 log-growth iterations. Evolution of the ribozyme was observed during the 70h evolution process on the chip. The ribozymes adapted and achieved progressively faster growth rates over time. The final evolved ribozyme contained 11 mutations which conferred 90-fold improvement in substrate utilization, coinciding with the applied selective pressure. The constellation of mutations that aroused during this evolution process and the corresponding phenotypic changes that were responsible for the adaptation were analyzed. The system thus, aids in accelerating evolution and also allows the experimenter to observe and manipulate adaptation.


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