Which statement best describes an operon in prokaryotic gene regulation?

• A. An operon is a segment of DNA found only in eukaryotic cells.
• B. An operon is a protein that binds to DNA to initiate transcription.
• C. An operon is a cluster of genes under the control of a single promoter and operator, transcribed together as a single mRNA.
• D. An operon is a single gene that is regulated independently of other genes.

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the concept of an operon. An operon is a functional unit of DNA in prokaryotic cells that consists of a cluster of genes regulated together. These genes are transcribed as a single mRNA molecule, allowing coordinated expression.
2. Step 2: Identify the components of an operon. It typically includes a promoter (where RNA polymerase binds to initiate transcription), an operator (a regulatory sequence where repressors or activators bind), and structural genes (coding for proteins).
3. Step 3: Compare the statements provided in the problem. Evaluate each statement based on the definition and characteristics of an operon. For example, operons are not exclusive to eukaryotic cells, nor are they proteins; they are DNA segments in prokaryotes.
4. Step 4: Focus on the correct description. The statement 'An operon is a cluster of genes under the control of a single promoter and operator, transcribed together as a single mRNA' aligns with the definition of an operon in prokaryotic gene regulation.
5. Step 5: Conclude that the correct answer is the statement describing the operon as a cluster of genes under unified control, transcribed together as a single mRNA. This reflects the coordinated regulation of gene expression in prokaryotes.