Gene expression can occur at several points along the pathway from DNA to RNA to proteins. In one example of gene expression, the protein insulin must be trimmed to a smaller size. How is this is an example of gene expression?

A. until the protein is trimmed, it is not useful to the cell
B until the protein is trimmed, transcription is blocked by repressor protein
C. until the protein is trimmed ribosomes are not active
D. until the protein is trimmed the shape of DNA blocks transcription