Final answer:
Histones lack sequence specificity due to epigenetic changes like acetylation, which relaxes the chromatin structure, leading to more accessible DNA for gene expression. These modifications do not change the DNA sequence but regulate the tightness of the DNA-histone binding.
Step-by-step explanation:
Histones lack sequence specificity due to the modifications that occur on their amino acid tails, which include acetylation. Acetylation of histones leads to the loose packing of nucleosomes, making DNA more accessible for transcription. These modifications fall under the concept of epigenetic changes, which do not alter the DNA sequence itself but instead influence chromatin structure and gene expression. Epigenetic changes like DNA methylation and histone acetylation or deacetylation change the spacing of nucleosomes, thereby regulating the activity of genes.
For example, the addition of acetyl groups to histone proteins decreases their positive charge, resulting in a relaxed binding of the DNA to the histones. This loosening allows for certain regions of the chromatin to become open to transcription; whereas, removal of these acetyl groups or the addition of methyl groups can cause the chromatin to become more condensed and less accessible to transcription machinery. Gene expression is thus tightly regulated by the balance of these epigenetic tags on histones and DNA.