<p>Chromo shadow domain is distantly related to chromo domain. It is always found in association with a chromo domain. </p><p>The CHROMO (CHRromatin Organization MOdifier) domain [<cite idref="PUB00005519"/>, <cite idref="PUB00004399"/>, <cite idref="PUB00004460"/>, <cite idref="PUB00004461"/>] is a conserved region of around 60 amino acids, originally identified in Drosophila modifiers of variegation.These are proteins that alter the structure of chromatin to the condensed morphology of heterochromatin, a cytologically visible condition where gene expression is repressed. In one of these proteins, Polycomb, the chromo domain has been shown to be important for chromatin targeting. Proteins that contain a chromo domain appear to fall into 3 classes. The first class includes proteins having an N-terminal chromo domain followed by a region termed the chromo shadow domain [<cite idref="PUB00004460"/>], eg. Drosophila and human heterochromatin protein Su(var)205 (HP1); and mammalian modifier 1 and modifier 2. The second class includes proteins with a single chromo domain, eg. Drosophila protein Polycomb (Pc); mammalian modifier 3; human Mi-2 autoantigenand and several yeast and <taxon tax_id="6239">Caenorhabditis elegans</taxon> hypothetical proteins. In the third class paired tandem chromo domains are found, eg. in mammalian DNA-binding/helicase proteins CHD-1 to CHD-4 and yeast protein CHD1.</p> Chromo shadow, subgroup