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.
Exothermic and endothermic reactions. When a chemical reaction occurs, energy is transferred to, or from, the surroundings-and there is often a temperature change. For example, when a bonfire burns it transfers heat energy to the surroundings.ndothermic reactions. These are reactions that take in energy from the surroundings. The energy is usually transferred as heat energy, causing the reaction mixture and its surroundings to get colder.