Final answer:
Nonspecific extra PCR products are usually caused by insufficient primer annealing temperature, which can result in primers binding to non-specific locations on the DNA template.
Step-by-step explanation:
Nonspecific extra PCR products can result from insufficient primer annealing temperature. During the Polymerase Chain Reaction (PCR), there are three main steps: denaturation, annealing, and extension. If the annealing temperature is not optimized, primers may bind non-specifically to the DNA template, leading to amplification of unintended products. It is essential that the annealing temperature is sufficiently high to ensure that primers bind only to the specific target sequences but not so high as to prevent primer binding altogether.
Though other factors like insufficient primer concentration, insufficient template DNA concentration, and insufficient dNTP concentration can affect PCR, they typically lead to different issues such as weak signals or incomplete extension rather than nonspecific products. The success of PCR relies heavily on the careful optimization of all components and conditions of the reaction.