Which of the following would be an example of a cis-acting eukaryotic gene regulatory element?

• A. Transcription factor
• B. Enhancer
• C. Mediator complex
• D. RNA polymerase

Answer: (B)

Verified step by step guidance

1. Understand the concept of gene regulation in eukaryotes, which involves various elements that control the expression of genes.
2. Differentiate between cis-acting and trans-acting elements. Cis-acting elements are DNA sequences located on the same molecule of DNA as the gene they regulate, while trans-acting elements are usually proteins that can regulate genes on different DNA molecules.
3. Identify examples of cis-acting elements, which include promoters, enhancers, and silencers. These are sequences that can increase or decrease the transcription of a gene located on the same DNA molecule.
4. Recognize that enhancers are specific DNA sequences that can increase the transcription of a gene. They are considered cis-acting because they are part of the DNA sequence itself and affect the expression of genes on the same DNA molecule.
5. Conclude that among the options given, 'Enhancer' is the correct example of a cis-acting eukaryotic gene regulatory element, as it is a DNA sequence that regulates gene expression on the same DNA molecule.