The core clock apparatus consists of nine genes so far identified 2." (though there are undoubtedly more to be discovered 4), yet controls a large part of the genome. In particular, the clock work and cell cycle regulatory system appear to in any of obvious question is whether variants the clock genes are associated with risk of breast cancer a question first addressed by Zhu et al who reported an association of a length fruitful isum in and risk. too soon to say how this line of inquiry will be.