Cytosine demethylation, active

This inability of fully functional receptor complexes to activate a given gene also occurs in normal cells. In new-born chicks, a single injection of oestradiol has a delayed effect on vitellogenin synthesis in liver. Having been exposed once to the hormone, second injections elicit an immediate response. It has been suggested that the first injection demethylates methyl cytosine residues within the hormone response element, thereby allowing receptor attachment [29]. 

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