From Wikipedia,
the free encyclopedia.
CpG islands are regions
of DNA near and in the
promoter of a
mammalian
gene where a large
concentration of
CpG sites exist. Unlike CpG
sites in the
coding region of a gene, in
most instances the CpG sites in
the CpG islands are unmethylated
if genes are expressed. This
observation led to the speculation
that methylation of CpG sites in
the promoter of a gene may inhibit
the
expression of a gene.
The usual formal definition of
a CpG island is a region with at
least 200
bp and with a GC percentage
that is greater than 50% and with
an observed/expected CpG ratio
that is greater than 0.6.
External Link:
M. D. Anderson Cancer Center
