CpG islands are often methylated. This may be because CpG island often contain promotor regions for genes (regions where transcription factors can bind and start transcription). They are methylated (as the hypothesis goes) to shut of gene expression, giving the cell another way to control gene expression. These controls are not a change in the DNA code, or the binding of a transcription factor therefore they are deemed "epigenetic."
Epigenetics
Re: Epigenetics
