Fig. 1: Model overview.

a Model procedure: A repeat RNA or DNA sequence is converted to a sticker-spacer model, with stickers comprised of self-complementary regions. Possible structures, including multimers, are then enumerated by either computational or analytical methods. Partition functions are then calculated, leading to a complete description of the equilibrium behavior of the system, including the equilibrium concentrations of multimers. The system is in the aggregation regime when concentrations remain constant or increase with multimer size. b Regimes of linker length: The system can exhibit qualitatively different behavior depending on the length of the inert linkers. For long enough linkers, adjacent stickers can bind; for short linkers, they cannot because of hairpin size constraints. Structures visualized using forna³⁷. c Regimes of sticker strength: For strong stickers, (almost) all of the sticker bonds are typically satisfied; for weak stickers almost none are; for intermediate strengths, the number of sticker bonds typically satisfied depends on a combination of the sticker strength and the multiplicity of structures in which a given number of stickers is bound.