Final answer:
Histone proteins that bind to highly transcribed areas of DNA are often acetylated on lysine residues, which helps to relax the DNA wrapping and promotes transcription.
Step-by-step explanation:
Histone proteins that bind to highly transcribed areas of DNA are often acetylated on lysine residues. This modification is crucial for the regulation of gene expression. The acetylation process is mediated by enzymes known as histone acetyltransferases (HAT enzymes), which add acetyl groups to the lysine residues on histones. This addition changes the charge on the histone proteins, making them less positive. As a result, the DNA wrapped around the histones is less tightly coiled, which enables transcription factors to access the DNA more easily and increases the level of gene transcription.
In contrast, regions of DNA that are highly methylated and associated with deacetylated histones are typically more condensed and transcriptionally inactive. This highlights the importance of these chemical modifications in controlling whether a gene is turned on or off. Histone acetylation is known for its role in unwinding nucleosomes and opening up chromatin for transcription, while deacetylation generally results in more condensed chromatin and reduced transcriptional activity.