Operons

The "on/off" switch for an operon is called the

• promoter

• repressor

• operator

• gene

For a repressible operon to be transcribed, which of the following must be true?

• corepressor must be present.

• RNA polymerase and the active repressor must be present.

• RNA polymerase must bind to the promoter, and the repressor must be inactive.

• RNA polymerase cannot be present, and the repressor must be inactive.

What is 1 in the diagram?

• RNA polymerase

• Inducer

• Repressor

• Operator

What is 2 in the diagram?

• RNA polymerase

• Inducer

• Repressor

• Operator

What is 4 in the diagram?

• RNA polymerase

• Inducer

• Repressor

• Operator

In the lac operon, the genes within the operon will be expressed if:

• lactose is absent in the cell

• galactose is present in the cell

• lactose is present in the cell

• glucose is absent in the cell

What is 5 in the diagram?

• RNA polymerase

• Inducer

• Repressor

• Operator

The trp operon in E. Coli is responsible for making 5 polypeptides involved in the tryptophan synthesis pathway. When tryptophan is present, it combines with the repressor protein to block the operator. What type of operon is trp?

• Repressible

• Inducible

The operon model was discovered in E. Coli and is almost exclusively found in ​ (a)   .

• prokaryotes

• eukaryotes

Which of the following statements regarding the trp operon is true?

• The operator region produces the mRNA that codes for the repressor.

• The regulatory gene is not transcribed in the presence of the repressor.

• Repressor proteins are inactivated by the presence of the repressor. .

• The trp operon is always activated unless deactivated by a repressor