DNA methylation and histone acetylation are examples of epigenetic modifications. Epigenetic modifications are heritable changes in gene expression that do not involve alterations to the DNA sequence itself. Instead, they involve modifications to DNA or histone proteins that can influence gene activity.
DNA methylation refers to the addition of a methyl group to the DNA molecule, usually at cytosine residues in a CpG dinucleotide context. This modification can result in gene silencing by inhibiting the binding of transcription factors and other regulatory proteins to the DNA, thus reducing gene expression.
Histone acetylation, on the other hand, involves the addition of an acetyl group to specific lysine residues on histone proteins. This modification generally leads to relaxed chromatin structure and increased accessibility of the DNA to transcription factors and other regulatory proteins. As a result, gene expression is often enhanced.
Both DNA methylation and histone acetylation play important roles in gene regulation, development, and various cellular processes. They are key mechanisms by which cells can modify gene expression patterns in response to environmental cues and developmental signals.