Center for Theoretical Biological Physics
Chemical and Biomolecular Engineering
Dean of Engineering
Dean of Natural Sciences
Physics & Astronomy
University of Virginia
“Modeling the Emergence of Clones in Populations (By Drawing Analogies with the Physics of Glasses) and the Adaptive Immune System of Bacteria (Called CRISPR)”
Tuesday, April 4, 2017
to 1:30 PM
1060 A/B BioScience Research Collaborative
6500 Main St.
Houston, Texas, USA
Abstract: I will present two population genetics stories where analogies from physics have been pivotal. First, I will talk about the emergence of clones in populations. Recombination reshuffles genetic material, while selection amplifies the fittest. If recombination is more rapid than selection, a population is a diverse mixture of genotypes. In the opposite regime, selection amplifies individual genotypes into large clones causing "clonal condensation." Clonal condensation is analogous to the freezing transition in the Random Energy Model. Here, I will derive the probability that two individuals are genetically identical. Next, I will speak about CRISPR -- the adaptive immune mechanism of bacteria. It takes snippets of exogenous genomes and builds up a memory of past infections. With a new infection, the memory is accessed, and in a successful outcome, the “invader” is neutralized. I will introduce a population dynamics model where immunity can be acquired and lost. This model has key parameters: the ease of acquisition and the effectiveness in conferring immunity.
Biography of Marija Vucelja:
Marija Vucelja is a theoretical physicist interested in soft condensed matter, computational physics and biophysics. She studied mixing and clustering of particles in flows; problems that are relevant for understanding the formation rain droplets and planetesimals, clustering of pollutants on water surfaces and appear in many industrial applications. She derived the compressibility of surface flows and described the aggregation-disorder transition of particles in flows. Using “chaotic mixing” she substantially accelerated particular Monte Carlo algorithms (the primary numerical tools for studying complex systems). Next, Marija examined the emergence of clones in populations. Drawing analogies between glassy systems and population dynamics she calculated the rate of coalescence (the probability of two individuals belonging to the same clone). Marija is working on inference problems in biophysics, the topology of structural glasses, and on developing efficient algorithms for studying glassy systems. Marija did her graduate studies at the Weizmann Institute. After the graduation, she moved to New York, and was a postdoc at the Courant Institute and later at the Rockefeller University. Currently, Marija is an Assistant Professor of Physics at UVa.