Which of the following is NOT a component of the master mix used in PCR?

The correct identification of the component that is not included in the master mix for PCR is based on an understanding of what constitutes a typical PCR reaction. The master mix typically includes Taq polymerase, which is the enzyme that synthesizes new DNA strands; dNTPs (deoxyribonucleotide triphosphates), which are the building blocks of DNA; and all necessary reagents that provide the optimal conditions for the reaction, such as buffer solutions.

Helices, although they refer to helicase enzymes that unwind DNA strands during replication, are not a part of the PCR master mix. In PCR, the denaturation step is accomplished by heating the reaction to separate the strands of DNA, eliminating the need for helicase. As such, the absence of helices in the PCR master mix reflects the unique characteristics of the PCR process compared to natural DNA replication mechanisms. This highlights the designed specificity of PCR, where high temperatures replace the function of helicases.