Friday, February 6, 2015

Science at the Edge Seminar

11:30 a.m., Room 1400 BPS Bldg.

Emergence and interference of clones in populations; glassy aspects of evolution

Marija Vucelja, The Rockefeller University

ABSTRACT: 

I will present a glimpse into the fascinating world of evolution and population genetics from the perspective of theoretical physics. Currently, the fields of evolution and population genetics are undergoing a renaissance, with the abundance of available sequencing data. In many cases, the existing theories are unable to explain the experimental findings. The least understood aspects of evolution are intrinsically quantitative and statistical, and we are missing a suitable theoretical description. It is not clear what sets the timescales of evolution, whether for antibiotic resistance, emergence of new animal species or the diversification of life. I will try to convey that physicists are invaluable in framing such pertinent questions. The emerging picture of genetic evolution is that of a strongly interacting stochastic system with large numbers of components far from equilibrium. In this talk, I plan to focus on the emergence and interference of clones in populations and glassy aspects of evolution.  Recombination of the genome reshuffles genetic material while selection acts to amplify the fittest genotypes. Rapidly recombining populations typically consist of many diverse genotypes. In facultatively recombining organisms selection amplifies fit genotypes and can form large clones. The occurrence of this "clonal condensation" depends on the ratio of recombination and selection rates and  the heritability of fitness. Clonal condensation is an important phenomenon, present in many populations. Traditional measures, such as linkage disequilibrium, do not describe this phenomenon. Our work provides a plausible qualitative explanation of clonal condensation. In the talk, I will point out the similarity between the clonal condensation and the freezing transition in the Random Energy Model of spin glasses. Guided by this analogy, I will derive one of the key quantities of interest: the probability that two individuals are genetically identical. This quantity is the analog of the spin-glass order parameter, and it is also closely related to the rate of coalescence: two individuals that are part of the same clone have a recent common ancestor. I will conclude with a summary of our present understanding of the clonal condensation phenomena and describe ongoing works on clonal interference. Lastly, I will point out similarities with physical phenomena in condensed matter physics, polymer physics, spin glasses and turbulence.

Shawna Prater / Secretary

Astrophysics Group

Michigan State University

567 Wilson Road, Room 3261

Biomedical Physical Sciences Bldg

East Lansing, MI 48824-2320

Ph: (517) 884-5601 Fax (517) 432-8802

[log in to unmask], [log in to unmask]

This e-mail may contain confidential information.  If you are not the intended recipient of this e-mail, you are hereby notified that any dissemination, distribution or copying of this message is strictly prohibited. If you received this message in error, please delete it immediately.