Final answer:
Translation is the molecular pathway that plays the biggest role in determining cellular phenotype.
Step-by-step explanation:
The molecular pathway that plays the biggest role in determining cellular phenotype is D) Translation.
Translation is the process in which a particular segment of DNA is copied into RNA (mRNA) by the enzyme RNA polymerase, and then the mRNA is used as a template to synthesize proteins.
Proteins are responsible for carrying out most of the cell's functions and determine the cell's phenotype.