Unlike prokaryotic cells whose genes are controlled mostly through ________, eukaryotic gene regulation occurs mostly through DNA binding proteins.

• A. Promoters
• B. Ribosomes
• C. Operons
• D. Introns

Answer: (C)

In prokaryotes, gene regulation is organized around operons, which are groups of genes transcribed together under a single promoter and controlled by a shared regulatory element. This arrangement lets bacteria rapidly coordinate the expression of several functionally related genes in response to environmental changes. In contrast, eukaryotic regulation relies mainly on DNA-binding proteins—transcription factors—that interact with promoters and distant enhancers to finely tune transcription, enabling more complex, cell-type–specific control across a larger genome. The other options don’t capture the hallmark bacterial mechanism: promoters are the initiation sites used in both domains; ribosomes govern translation rather than transcriptional control; introns are noncoding sequences removed during RNA processing and aren’t the primary means of prokaryotic regulation.