1) Directivity 2) Radial asymmetry 1) Directivity 
[molecular biology] Directionality, in molecular biology and biochemistry, is the end-to-end chemical orientation of a single strand of nucleic acid. The chemical convention of naming carbon atoms in the nucleotide sugar-ring numerically gives rise to a 5′-end and a 3′-end (usually pronounced `five prime end` and `three prime end`). The...
the property of being directional or maintaining a direction