Design through the Looking Glass

You don't have to hold an amino acid up to a mirror to see its mirror image. Amino acids (except for one, glycine) come in pairs, like gloves, on the real-world side of the looking glass. So do the sugars used in DNA and RNA; they are assigned a "handedness" based on conventional rules of describing their orientation in 3-D space. In all other physical respects, chemical and thermodynamic, they are identical in their activity. This makes them difficult to separate.

The phenomenon is known as...