A mutation in the IGF2 gene in pigs results in a threefold increase in the transcriptional activity of this gene in muscle cells; therefore, these pigs are leaner and more muscular. Because this mutation is in the noncoding region of the IGF2 gene, we can infer that:

A) the IGF2 gene is a prokaryotic gene.
B) the IGF2 gene is present only in muscle cells but not in adipose (fat) cells.
C) the mutation changes the amino acid sequence of the IGF2 protein.
D) the mutation alters the regulatory region of the IGF2 gene.
E) less IGF2 protein is synthesized in the muscle cells of these pigs.