Seminars

How might systematic chiral or left-right (L/R) asymmetry of the body plan originate in multicellular animals and plants? Fundamental principles (of symmetry and statistical mechanics) indicate that usual biological mechanisms -- diffusion and gene regulation -- do not suffice to implement the "right-hand rule" for (e.g.) the third body axis in a developing embryo. This requires that, somehow, the microscopic handedness of biological molecules must be brought up to macroscopic scales.

There are many independent examples of left/right specification in varied organisms: human brain, C. elegans, molluscs, drosophila, Arabidopsis plant roots -- bacteria too -- and vertebrate internal organs... Only in the last-mentioned case is there an accepted answer.

It appears from experiments, in any case where there is partial understanding at the cellular/molecular level, the mechanism it always involves the cytoskeleton (actin or microtubules, which are semi macroscopic fibers from our viewpoint). Because of (1) the mentioned role of symmetry, and (2) the involvement of molecular motors (forces and motions) the left-right problem seems especially appropriate to be studied by physicists.