At any given time, most of the roughly 30,000 genes that constitute the human genome are inactive, or repressed, closed to the cellular machinery that transcribes genes into the proteins of the body. In an average cell, only about one in ten genes is active, or expressed, at any given moment, with its DNA open to the cell' transcriptional machinery.

Researchers at the University of Alberta, in Edmonton, Canada, have announced the completion of the first draft of the human metabolome, the chemical equivalent of the human genome.