The origin of replication (also called the replication origin) is a particular sequence in a genome at which replication is initiated.
It is the interaction of two or more substances, resulting in chemical changes in them. Chemical reactions take place when some kind of energy is supplied to them. The supplied energy may be in the form of heat, light or mechanical shaking for proper contact between the reactant molecules or electricity.
Driving Forces and Gibbs Free Energy. Some reactions are spontaneous because they give off energy in the form of heat (H < 0). Others are spontaneous because they lead to an increase in the disorder of the system (S > 0). Calculations of H and S can be used to probe the driving force behind a particular reaction.