Functionally Related Genes in Bacterial Cells Are Frequently Clustered Together

Multiple Choice

Functionally related genes in bacterial cells are frequently clustered together as a single transcriptional unit termed an operon. A typical operon includes several structural genes, a promoter for the structural genes, and an operator site to which the product of a regulator gene binds.
-What is the difference between a structural gene and a regulator gene?

A) Structural genes are transcribed into mRNA, but regulator genes aren't.
B) Structural genes have complex structures; regulator genes have simple structures.
C) Structural genes encode proteins that function in the structure of the cell; regulator genes carry out metabolic reactions.
D) Structural genes encode proteins; regulator genes control the transcription of structural genes.