(operon model) A theory to explain how gene activity is regulated, proposed by F. Jacob and J. Monod in 1960. The theory is well substantiated for prokaryotes but there is little evidence that it is directly applicable to eukaryotic cells. The operon model shows how messenger RNA synthesis, and thus the quantity of enzymes present, may be regulated. By controlling the latter, the system as a whole provides a method of coordinating and regulating cell metabolism at the level of transcription. A parallel model, taking into account the very different organization of chromosomal DNA, has since been proposed for eukaryotes (see repeated sequence ). See also operon. |
