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.
Spontaneous reactions occur without any net input of energy. Many factors influence whether a reaction is spontaneous, including whether the reaction is exothermic or endothermic. Exothermic reactions that result in increased disorder, or entropy, will always be spontaneous.