Right and Left-Handed Symmetry in Nature

Most people have their hearts not in the middle of their bodies, but on the left-hand side. In contrast, a DNA double helix, a triple helix of collagen, and a spirals of globular proteins all have a right-handed structure. In engineering, except in some very special cases like the left-hand pedal of a bike, only right-handed screws are used. Why  

Let s start with engineering. A left-handed thread is no worse than a right-handed one. However, imagine a child s do-it-yourself kit where right-handed screws and nuts are mixed up with left-handed ones. The syrmnetry is, therefore, preserved. But it is quite awkward to play with, to put it mildly This awkwardness comes from the instability of the symmetrical state. The direction in which the symmetry was broken (right-handed screws) was chosen more or less by accident in the past. However, now it is 

Many more fascinating details about the left-right asymmetry can be found in the book [46]. 

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