Fig. 3.

a Relationship between contraction of the center filament (cyan) of an SC-like tripartite ribbon and twisting in the outer axes (red) if they are unable to contract (i.e., if their arc length is constant). In this example simulation, with a radius set to 100 nm and original length of 25 μm, a 1 % contraction in CE length (arrow) results in approximately 5.6 full LE twists, approx. 4.4 μm apart. The original position of the right end is indicated by a green line. Full-length movie of this simulation is shown in the Electronic Supplementary Material (movie 2). b 3D-SIM image of a mouse pachytene SC stained with antibodies against Sycp3. Twisting is apparent at a pitch of approx. 2 μm per full turn. Scale bar: 0.5 μm