DNA replication begins when something called Helicase (an enzyme) unwinds the helix structure of the DNA. It does this so that Primase can then come along and set down an RNA primer.
An area with unifying characteristic is called as a region. The region is a broad geographic area, which is differentiated from other because of the similar features. In a region one or more than one types vegetational climax might be present. It is the continuous and extensive part of the surface. The area in a region is indefinite.
Hence, the given blank can be filled with region.
Water molecule, skin cell, E. Coli Bacteria, grain of salt, human
