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.
Chemical reactions involve rearrangement of the atoms and produce. new substances in this process. For example, in the above picture, just the mixing of two substances can cause. the chemical reaction to occur. Chemical Reactions are everywhere in nature. The process by which the plants make their own food is called photosynthesis.