Is nucleoside-triphosphate delivery to RNA or DNA polymerase active or passive?
The amount of dNTPs is so important and sensitive the level of dNTPs should be optimum  not lower or higher. Lower amounts lead to insufficiency  and higher amounts lead to increased mutation rates. Also, this optimum amount of dNTPs should last for a couple of minutes to supply dNTPs needed for replication. The delivery of dNTPs is due to molecular signalling &amp; stochastic diffusion.



http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2847218/

"Eukaryotic cells contain a delicate balance of minute amounts of the four deoxyribonucleoside triphosphates (dNTPs), sufficient only for a few minutes of DNA replication. Both a deficiency and a surplus of a single dNTP may result in increased mutation rates"



http://onlinelibrary.wiley.com/doi/10.1111/j.1349-7006.2010.01719.x/pdf

"Optimization of intracellular concentrations of dNTPs is critical for
the fidelity of DNA synthesis during DNA replication and repair
because levels that are too high or too low can easily lead to
increased rates of mutagenesis"



http://www.nature.com/ncb/journal/v14/n7/full/ncb2540.html

"Production of deoxyribonucleotide triphosphates (dNTPs) is essential for DNA synthesis during replication and repair, and abnormal or imbalanced dNTP levels increases mutation frequency. Pagano and colleagues now demonstrate that the SCF-cyclin F ubiquitin ligase controls dNTP production during the cell cycle and following genotoxic stress"



http://www.ncbi.nlm.nih.gov/pubmed/22234185

"alterations in dNTP pools are associated with increased mutagenesis, genomic instability and tumourigenesis"