a process of amplifying a nucleic acid sequence by a procedure involving a polymerase chain reaction or a ligase chain reaction . the process involves repeated cycles of steps including a nucleic acid denaturing step and a nucleic acid synthesis step , the synthesis step being carried out under the action of an enzyme . the denaturing step and the synthesis step are carried out in different denaturing and synthesis reaction zones , respectively , and , during the repeated cycles , the enzyme is maintained in isolation from the denaturing reaction zone , and conditions or reagents required for the denaturing step are maintained in isolation from the synthesis reaction zone to the extent that the reagents and conditions required for denaturing do not impede the synthesis reaction to a substantial extent . the use of separate zones for the steps of the reactions means that an enzyme that is destroyed or degraded by the reagents and conditions required for denaturing may be used in the reaction . moreover , the use of multiple zones means that inexpensive equipment may be used for the process .