BSC 310 Ch 7 Practice Questions

BSC 310 Ch 7 Practice Questions Which of the following are genetic elements found in an operon? a. operator region b. structural genes c. promoter d. all of the above - Answer- all of the above Which of the following statements regarding operons is true? a. Inducible operons are transcribed only when they are activated. b. Repressible operons are always transcribed unless they are deactivated by a repressor. c. The structural genes of an operon typically have the same biochemical function in the cell. d. All of the above statements are true. e. None of the above statements are true. - Answer- d. all of the above statements are true where does the activation and repression of an operon occur? - Answer- at the operator region What does the inducer bind to in the lac operon system? a. the promoter region of the DNA b. repressor proteins c. RNA polymerase d. the operator region of the DNA - Answer- b. repressor proteins Which genetic element codes for the repressor protein for the lac operon? a. the promoter region b. lacY c. the operator region d. the regulatory gene e. lacZ - Answer- d. the regulatory gene Which of the following statements regarding the lac operon is true? a. Galactose is an inducer of the lac operon. b. The operator region codes for the structural genes involved in lactose metabolism. c. The repressor proteins bind to the operator, preventing RNA polymerase from transcribing the structural genes. d. When lactose is available, the repressor proteins are inactive. - Answer- c. The repressor proteins bind to the operator, preventing RNA polymerase from transcribing the structural genes. When is the regulatory gene transcribed? a. It is transcribed only in the presence of lactose. b. It is transcribed only when the regulatory protein is not bound to the operator. c. It is transcribed only in the absence of lactose. d. It is always transcribed. - Answer- d. It is always transcribed. Which of the following statements regarding the induction of the lac operon is true? a. Allolactose serves as an inducer. b. The inducer acts by turning off the repressor. c. Induction of the operon ceases when lactose is absent from the system. d. All of the above statements apply. e. None of the above statements apply. - Answer- d. All of the above statements apply. the lac operon is a(n) _________ operon, meaning that the genes usually are/are not transcribed - Answer- inducible, are not what is the inducer for the lac operon? How does it work? - Answer- allolactose works by binding to the repressor proteins inhibiting their ability to bind to the operator region of the lac operon, therefore allowing RNA Polymerase to transcribe the structural genes of the lac operon Which of the following statements regarding the trp operon is true? a. The trp operon is always activated unless deactivated by a repressor. b. The regulatory gene is not transcribed in the presence of the repressor. c. The operator region produces the mRNA that codes for the repressor. d. Repressor proteins are inactivated by the presence of the repressor. - Answer- The trp operon is always activated unless deactivated by a repressor. What is the role of tryptophan in the trp operon? a. It causes the transcription of the regulatory gene. b. It activates the repressor proteins. c. It is needed to produce the structural genes. d. It binds to the operator region. - Answer- It activates the repressor proteins. Why is the transcription of structural genes of the trp operon turned off in the presence of tryptophan? a. Tryptophan has no effect on the transcription of the structural genes.