What effect do acetyl groups have on histones?

Acetyl groups have a significant effect on the structure and function of histones, which are proteins around which DNA is wrapped to form nucleosomes. The addition of acetyl groups to histones is a process called acetylation, which leads to the neutralization of the positively charged amino acids in the histone tails, primarily lysines.

The positive charge on histones is important for their interaction with the negatively charged DNA, facilitating the compact structure of chromatin. However, when acetyl groups are added, they modify the chemical properties of these lysine residues, reducing their positive charge. This less positive state diminishes the overall affinity between the histones and DNA, leading to a more relaxed chromatin structure.

This relaxed state allows for greater accessibility of transcription machinery to the DNA, promoting gene expression. Thus, the correct answer highlights how the introduction of acetyl groups makes histones less positive, ultimately impacting chromatin structure and gene regulation.