Recorded 16 September 2025. Alexei A. Kornyshev of Imperial College London presents "When Polyelectrolytes Think: From Electrochemistry to Molecular Genetics (Stochastic Polyelectrolyte Dynamics in Pairing Homologous Genes)" at IPAM's Embracing Stochasticity in Electrochemical Modeling Workshop. Abstract: DNA in aqueous solution is a highly charged polyelectrolyte — in fact, a kind of electrostatic bomb — with every phosphate group on its sugar–phosphate backbone carrying a negative charge. These charges are partially neutralized by specifically adsorbing counterions such as calcium or magnesium, or by stronger polycations such as cobalt-hexammine or spermine. Additional screening comes from the surrounding physiological salt solution. Yet the resulting charge distribution is not perfectly uniform: the local distortions of the double helix depend on sequence, and these distortions are correlated with electrostatics. This talk will show how the accumulation of such sequence-dependent distortions provides a physical mechanism by which homologous double-stranded DNA segments recognize and pair with one another in solution — a phenomenon at the heart of homologous recombination. Homologous recombination is essential for gene repair and genetic diversity, but the initial alignment of homologous chromosomes has long remained mysterious. While proteins facilitate the recombination process, experiments demonstrate that DNA can pair without them. Theory suggests that intrinsic structural and electrostatic fluctuations of DNA allow homologous sequences to distinguish each other from nonhomologous ones. Recognition need not mean necessarily attraction versus repulsion, but could be a difference in the strength of repulsion depending on environment. What, then, drives pairing? We will explore the interplay of counterion condensation, osmotic stress, and global confinement as possible drivers. The talk will describe the stochastic dynamics of homolog pairing both in free electrolytic solution and under confinement mimicking the cellular environment. In doing so, it will highlight how concepts from polyelectrolyte physics and electrochemistry provide fresh insight into a central problem of molecular genetics. Learn more online at: https://www.ipam.ucla.edu/programs/workshops/workshop-i-embracing-stochasticity-in-electrochemical-modeling/?tab=overview