Final answer:
Altered methylation states are commonly found in the CpG islands of DNA, leading to gene silencing and playing a crucial role in the regulation of gene expression. These patterns are often observed in various diseases, including cancer, and are the focus of research aiming at reversing these epigenetic changes for therapeutic purposes.
Step-by-step explanation:
Altered methylation states are frequently observed in regions of the DNA referred to as CpG islands. These are areas with a high density of cytosine and guanine dinucleotides located mainly in the promoter regions of genes. The addition of a methyl group to the cytosine nucleotide, a process known as DNA methylation, can lead to gene silencing and is a key component of epigenetic regulation.
In cancer cells, silenced genes often display methylation of cytosine residues in these CpG islands. These alterations, paired with changes such as histone deacetylation, result in compact, transcriptionally inactive chromatin. This is also seen in some inherited conditions where genes are imprinted, meaning they are silenced in gametes and remain silent in the offspring. The environment, including factors such as parental diet, can influence gene expression through changes in DNA methylation patterns.
Researchers are investigating methods to reverse these epigenetic modifications to re-establish normal gene function in diseases such as cancer, by targeting the enzymes like DNA methyltransferases and histone deacetylases responsible for these changes.