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.
In an exothermic reaction energy is given out, usually in the form of heat. This can often be detected by a rise in temperature. Exothermic reactions are very common. For example: 1  burning fuels. 2  respiration. 3  in neutralisation reactions, such as reacting an acid with a metal or an alkali.