Histones are proteins that regulate gene expression by binding to DNA and controlling which regions are exposed to be expressed. Histones bind to DNA at a neutral pH via their positively charged lysine residues, but acetylation of histones leads to the dissociation of the DNA-Histone complex. Covalent modification of lysine's ammonium group by acetylation results in an overall _______________ charge of the histone binding region.

• A. Positive.
• B. Neutral.
• C. Negative.

Answer: (B)

Verified step by step guidance

1. Understand the role of histones: Histones are proteins that help in the regulation of gene expression by binding to DNA. They do this through their positively charged lysine residues, which interact with the negatively charged phosphate groups of DNA.
2. Recognize the effect of acetylation: Acetylation is a covalent modification where an acetyl group is added to the lysine residues of histones. This process neutralizes the positive charge of the lysine's ammonium group.
3. Consider the charge change: When lysine residues are acetylated, the positive charge is neutralized, leading to a reduction in the overall positive charge of the histone binding region.
4. Analyze the impact on DNA binding: The neutralization of the positive charge weakens the interaction between histones and DNA, causing the DNA-histone complex to dissociate more easily.
5. Conclude the charge state: After acetylation, the histone binding region becomes neutral in charge, which is why the correct answer is 'Neutral'.