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.
All four phase changes require either an increase in temperature, a decrease in pressure or both, and they are referred to as endothermic reactions because they absorb heat. The increase in heat leads to an increase in kinetic energy among the molecules of the substance.