Physics - CPLC Calendar

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Biological Physics Seminar (CPLC): "Epistasis and genetic variation in adaptability in yeast"

SpeakerDr. Sergey Kryazhimskiy, University of California San Diego
Date Mar 10, 2017
Time 2:00 pm  
Location 280 MRL, 104 S. Goodwin
Cost N/A
Sponsor Dr. Seppe Kuehn
Contact Becky McDuffee
Phone 217-300-0898
Event type Seminar/Symposium
Views 15

Since the dawn of population genetics, evolutionary biologists have been interested in genetic interactions (also called epistasis) between mutations because some types of epistasis can lead to interesting phenomena like historical contingency and speciation. However, other types of genetic interactions may have little influence on the evolutionary process. How prevalent are different types of epistasis? I will discuss two experiments that help us understand the statistical structure of epistasis and how it affects evolutionary trajectories. The basic idea is to start evolution from genetically distinct strains of an organism (we use yeast S.cerevisae) and to understand how initial mutations affect the evolutionary outcomes. We find that most initial mutations have surprisingly little effect on the pool of further adaptive mutations. However, we found one exception to this rule. Aside from this one mutation, epistasis between most mutations appears to be of the "diminishing returns" type, such that the beneficial effect of an adaptive mutation is systematically smaller in fitter genetic backgrounds, but does not change sign. As a consequence, fitness evolution follows predictable trajectories even though adaptation at the genetic level is highly random.    

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