Mathematics Colloquia and Seminars

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The Escherichia coli genome is encoded in a large circular chromosome. After replication, the two resulting DNA circles are interlinked. Returning the circular DNA chains to an unlinked monomeric state is essential to cell survival. The cell uses enzymes such as type II topoisomerases to solve this problem. The Sherratt Lab has shown that in E. coli, in the absence of the type II topoisomerase topo IV, site-specific recombinases XerC and XerD mediate chromosome unlinking. We use knot theory, low-dimensional topology, and computer simulations to characterize the mechanism by which these enzymes simplify the topology of DNA. We show definitively that there is a unique shortest pathway of unlinking by Xer recombination that strictly reduces the complexity of the links at every step.

Reception to follow in the Alder Room