5. What molecule serves as a co-repressor for the trp operon? a) Ribosome c) trpR e) Glucose b) Tryptophan d) ?-galactosidase 6. Which of the following statements about the "glucose effect" is true? a) The activity of adenylcyclase is inhibited by glucose. b) Cyclic AMP levels increase when glucose is present. c) CAP activates transcription of the lac operon when glucose is present. d) Cells will metabolize lactose when glucose is present. 7. Attenuation of the trp operon does not include which of the following? a) trpR c) ribosome e) all are needed b) tryptophan d) RNA polymerase 8. The lac operon, when using lacI, is regulated by a(n) a) activator and inducer c) activator and co-repressor b) repressor and inducer d) repressor and co-repressor 9. The trp operon is regulated by a(n) a) activator and inducer c) activator and co-repressor b) repressor and inducer d) repressor and co-repressor 10. Pairing of which sequence regions within trpL actually result in the transcriptional termination of the trp operon? a) 1 and 2 b) 2 and 3 c) 3 and 4 d) 1 and 4
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Which of the following statements is true regarding the trp operon? A) Tryptophan binds to the operator to promote the binding of RNA polymerase. B) The trp operon includes an operator that acts as the binding site for RNA polymerase. C) When tryptophan is in short supply, the trp operon is expressed. D) The operon's genes are transcribed when tryptophan is bound to the trp repressor.
Dominador T.
1- What happens in the lac operon when both lactose and glucose are present in the environment? a) Transcription of the lac operon structural genes will occur. b) Transcription of the lac operon structural genes will occur but at a very slow rate. c) Transcription of the lac operon structural genes will occur at an increased rate. d) Transcription of the lac operon will not occur because the inducer is not present in the environment. e) Transcription of the lac operon will not occur because of catabolite repression. 2- Which statement about catabolite repression is false? a) Glucose is the preferred energy source for E. coli and represses the utilization of other sugars. b) The CAP protein is involved in catabolite repression of the lac operon. c) RNA polymerase is the effector molecule that enables CAP to bind to the promoter. d) The CAP protein and its effector molecule exert positive control over the transcription of the lac operon. e) High glucose concentrations decrease the intracellular concentration of the effector molecule of the CAP protein. 3- Which of the following substances is the inducer for the lac operon? a) Lactose b) Tryptophan c) cAMP d) Glucose e) CAP
Madhur L.
Recall that the trp repressor binds to a site in the operator region of tryptophan-producing genes when tryptophan is abundant, thereby preventing transcription. What would happen to the expression of the tryptophan biosynthetic enzyme genes in the following scenarios? Fill in the blanks with one of the following phrases:never be expressed/always (constitutively) be expressed a. The cell produces a mutant trp repressor that cannot bind to the operator. The enzyme genes will ________________. b. The cell produces a mutant trp rcpressor that binds to its operator site even if no tryptophan is present. The enzyme genes will ___________________. c. The cell produces a mutant sigma factor that cannot bind the promoter region. The enzyme genes will _____________________ . d. Elongation of the leader sequence is always stalled a fter transcription of region 1. The enzyme genes will _____________________ .
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