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.
Most chemical reactions involve the breaking and formation of chemical bonds. It takes energy to break a chemical bond but energy is released when chemical bonds are formed. If more energy is released than consumed, then the chemical reaction evolves heat and is said to be exothermic. On the other hand if the reaction consumes more energy than it releases then the reaction absorbs heat and is said to be endothermic. Most reactions are exothermic. The amount of heat generated by a reaction can be quantified. The quantity that specifies the amount of heat is known as the enthalpy . If is positive then the reaction is endothermic and if it is negative the reaction is exothermic.