In 1965, Francois Jacob and Jacques Monod shared in the Nobel Prize in medicine for their pioneering work in explaining how genes can be selectively turned on and off. They developed a model, called the Lac operon model, which proposed a mechanism to explain how bacteria are able to limit the synthesis of the enzymes needed for bringing lactose into the cell and matabolizing it to only those time when lactose is present in the environment. In their model, theses genes are turned off when a protein called the lac repressor is bound to the DNA, just upstream of the genes that code for these enzymes. The presence of the repressor blocks RNA polymerase from transcribing the genes into messenger RNA.

Obtain a copy of Bell and Lewis's article. These compares structures for both the operator bound repressor and the IPTG inducer bound repressor.

Place the three jpeg files in a folder named username_lab4, convert it to a zip file and email it to me.