Essential Genetics 6th Edition by Daniel Hartl

Exercise 5

In studies of the operator region of an inducible operon in E. coli , the four constructs shown below were examined for level of transcription in vitro. The number associated with each construct is the relative level of transcription observed in the presence of the repressor protein. The symbols E, B, H, and S stand for the restriction sites Eco RI, Bam HI, Hind III, and Sac I. Construct (a) is the wildtype operator region, and in parts (b-d) the open boxes indicate restriction fragments that were deleted. What hypothesis about repressor-operator interactions can explain these results? How could this hypothesis be tested?