CG islands

CG islands are also known as CpG islands to distinguish them from the occasional CG base pair. The C stands for the nucleotide cytosine and the G stands for the nucleotide guanine. They are short regions that are rich in the CG sequence. They are often found around the promoters for the housekeeping genes of the cell, which are the genes responsible for the transcription of the most essential proteins in the cell (Alberts, et al., 470). Significantly, they are often found de-methylated in normal cells, but hypermethylated in cancer cells.