Question

1. Consider the following scenario: The bacterium Edvardobacillus tsvangirai (or Et for short) has an operon named the “car” operon with the following parts

• Promoter

• Operator

• Four Structural genes that specify four enzymes that work together to break down an antibiotic called CAR-M inside this bacterium

The car operon is “controlled” by its own repressor protein. The repressor has a cleft which matches the shape of CAR-M.

Answer the question below based on the scenario above and your knowledge of operons (and their regulation).

- Explain whether car operon genes would be expressed when the bacterium Et is NOT exposed to CAR-M by describing what happens to car operon when the bacterium is not exposed to the antibiotic.

Answer 1

• When the bacterium is not exposed to the antibiotic, the repressor molecule would remain bound to the operator region of CAR-M operon. This would block transcription of CAR-M operon genes.
• When antibiotic is present in the medium, then it would bind to the repressor molecule. This detaches the repressor from operator of CAR-M operon, and thus transcription of the operon genes is allowed.

When the repressor bind to operator, RNA polymerase enzyme cannot proceed beyond the operator region, thus halting the process of transcription.