In bacteria, a cluster of functionally related genes that are transcribed together is called an ______.

In bacteria, a cluster of functionally related genes that are transcribed together is called an ______.

• A. Promoter
• B. Operator
• C. Plasmid
• D. Operon

Answer: (D)

In bacteria, functionally related genes that are transcribed together are organized into an operon. An operon is a transcriptional unit that includes the promoter (where RNA polymerase binds to start transcription), the operator (a regulatory site where a repressor can bind to turn transcription on or off), and the structural genes themselves. The whole operon is transcribed as a single mRNA molecule, meaning all the genes are expressed together in a coordinated fashion. This setup enables rapid and efficient regulation of groups of related genes, such as those needed for metabolizing a particular nutrient, like in the classic lac operon example. A plasmid, by contrast, is just an extra-chromosomal DNA molecule that can carry additional genes, and the promoter or operator alone are merely regulatory components, not the entire gene cluster themselves.

In bacteria, functionally related genes that are transcribed together are organized into an operon. An operon is a transcriptional unit that includes the promoter (where RNA polymerase binds to start transcription), the operator (a regulatory site where a repressor can bind to turn transcription on or off), and the structural genes themselves. The whole operon is transcribed as a single mRNA molecule, meaning all the genes are expressed together in a coordinated fashion. This setup enables rapid and efficient regulation of groups of related genes, such as those needed for metabolizing a particular nutrient, like in the classic lac operon example. A plasmid, by contrast, is just an extra-chromosomal DNA molecule that can carry additional genes, and the promoter or operator alone are merely regulatory components, not the entire gene cluster themselves.