Figure 2. Zippering reduces pairing fidelity.

(A) pairing outcome, plotted as in Figure 1A, for a typical simulation run with parameters k_unpair_correct 0.001 k_unpair_incorrect = 0.01. As illustrated by these two images, even with a ten-fold difference in affinity, incorrect pairing can be extensive. (B) Pairing discrimination, given as the ratio of correctly paired loci to incorrectly paired loci, plotted as a function of the unpairing rate (k_unpair) for incorrect versus correct loci. Simulations were run using k_unpair_correct of 0.001. (Circles) results of 100 simulations for each set of parameters. (Line) the expected discrimination if all loci paired and unpaired independently. Deviation of the simulation results below the line indicate that when loci are linked together into a polymer, discrimination is reduced, presumably due to avidity effects that prevent recently unpaired loci from diffusing apart.