CpG methylation patterns

CpG methylation involves adding chemical groups called methyl groups to specific DNA sites where a cytosine nucleotide is followed by a guanine nucleotide, known as CpG sites. This modification can influence gene activity—typically turning genes off or reducing their expression—by making the DNA less accessible for the cell's machinery. Methylation patterns vary across the genome and can change over time or in response to environmental factors, playing important roles in development, cell identity, and disease processes like cancer. Essentially, CpG methylation acts as an epigenetic marker that helps regulate how genes are turned on or off without altering the underlying DNA sequence.