Final answer:
The ingredient in a PCR cycle that would not limit the production of PCR products when run indefinitely is the buffer. The buffer is not consumed like primers, dNTPs, or the template; it simply provides necessary conditions for the PCR to take place.
Step-by-step explanation:
The correct option : b
In a typical PCR reaction setup, several components are crucial: DNA template, primers, DNA polymerase, dNTPs (deoxynucleotides), and buffer solution. Over many cycles, primers (A) may run out because they are consumed in each cycle for new strand synthesis. The template (C) DNA can also become limiting as it serves as the original source of the sequence to be amplified. dNTPs (D) serve as building blocks for new DNA strands and can be depleted over time. DNA polymerase (added at the beginning) must remain active but will not run out, as it is an enzyme that is not consumed in the reaction.
The PCR buffer provides the suitable conditions (pH, salts, etc.) for the reaction to proceed, but it is not consumed like the other reagents. Thus, the buffer will not limit the amount of product formed in an indefinitely running PCR.The buffer solution is added to maintain the optimal pH and ionic conditions for the DNA polymerase to function efficiently throughout the PCR cycles. However, it does not directly contribute to limiting the amount of PCR products produced.