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.
When an exothermic reaction takes place, the reaction mixture gives out heat because... 1  more energy is released when new bonds are formed than is taken in when existing bonds in the reactants are broken. 2  the radiation energy produced by the reaction has to be got rid of via diffusion.