Jacob and Jacques Monod, who won the Nobel Prize in 1965 for their work on the lac operon, were the fellows who really put gene regulation on the map, working out the mechanisms behind switching genes off and on in response to environmental cues. I always talk about their work on day one of my developmental biology courses; everything else in molecular genetics and development are built on the foundation they laid down.
And now Le prix Nobel et résistant François Jacob est mort (Monod died in 1976).
By the way, in addition to being a great scientist, Jacob was also a great atheist. This is a loss to all of us.