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.
Reactions that give out heat energy are called exothermic reactions.. These reactions feel warm to the touch. If a reaction is highly exothermic it may be dangerous to actually touch and feel it. Explosion are very exothermic reactions.