Practice Questions

TLS Online TPP Program

#Question id: 3982

The diagram below represents a hypothetical operon in the bacterium E. coli. The operon consists of two structural genes (A and B) that code for the enzymes A-ase and B-ase, respectively, and also includes P (promoter) and O (operator) regions as shown.

When a certain compound (X) is added to the growth medium of E. coli, the separate enzymes A-ase and B-ase are both synthesized at a 50-fold higher rate than in the absence of X (which has a molecular weight of about 200). Which one of the following statements is true of such an operon?

#Unit 3. Fundamental Processes

Adding X to the growth medium causes a repressor protein to be released from the O region.
Adding X to the growth medium causes a repressor protein to bind tightly to the O region.
Synthesis of the mRNA from this operon is not changed by the addition of compound X.
The mRNA copied from this operon will be covalently linked to a short piece of DNA at the 5' end.