A scientist clones a regulatory gene that is involved in controlling the expression of other genes and discovers that the regulatory gene encodes an enzyme that acetylates histones. It is likely that this enzyme regulates gene expression by __________.

• A. causing tighter packing of the chromatin at the target gene, thereby inhibiting transcription
• B. causing looser packing of the chromatin at the target gene, thereby inhibiting transcription
• C. causing tighter packing of the chromatin at the target gene, thereby enhancing transcription
• D. causing tighter packing of the chromatin at the target gene, thereby inhibiting translation
• E. causing looser packing of the chromatin at the target gene, thereby enhancing transcription

Answer: (E)

Verified step by step guidance

1. Understand the role of histone acetylation: Histone acetylation is a process where acetyl groups are added to histone proteins. This modification is known to affect the structure of chromatin, which is the complex of DNA and proteins in the nucleus.
2. Recognize the effect of acetylation on chromatin structure: Acetylation of histones typically leads to a looser chromatin structure. This is because the addition of acetyl groups neutralizes the positive charges on histones, reducing their affinity for the negatively charged DNA.
3. Connect chromatin structure to gene expression: Looser chromatin structure allows transcription machinery better access to DNA, facilitating the transcription process. Therefore, acetylation generally enhances gene expression.
4. Evaluate the options given in the problem: The correct option should reflect the effect of histone acetylation on chromatin structure and gene expression. The option 'causing looser packing of the chromatin at the target gene, thereby enhancing transcription' aligns with the known effects of histone acetylation.
5. Conclude the reasoning: Based on the understanding of histone acetylation, the enzyme encoded by the regulatory gene likely regulates gene expression by causing looser packing of chromatin, which enhances transcription.