Areas of DNA which consist mostly of the base pair sequence CGCGCGCG (alternating cytosine and guanine nucleotide bases) that are usually found upstream of many genes and are thought to help regulate gene expression. They are often methylated (have methyl groups attached to the DNA segments). These act as promoter regions in genes, thus the "p" in their name.

From the BioTech Dictionary at For further information see the BioTech homenode.