Gene Repression

A review of the details of mitosis reminds us that all the cells of a body have the same genetic material-the same DNA. Yet, different cells do different things, and the same cells sometimes do different things at different times. Certain genes, then, can be turned on at one time and turned off at another time. An explanation of gene repression was first developed by Francois Jacob and Jacques Monot at the Pasteur Institute. In working with E. coli, Jacob and Monot determined that there is a structural gene and an operator gene, which together compose a genetic unitc alled an operon. Whether the operon is able to function or not depends on another gene called a repressor gene. Of course, each of these genes carries out its work by the production of enzymes. In 1965 Jacob and Monot were awarded the Nobel prize for their work in this field.