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Unformatted text preview: Klug, Concepts of Genetics 8/e Chapter 16 MEDIA REVIEW QUESTIONS 1. Which term is used to describe enzymes that are produced only when specific substrates are present in the environment? a. Constitutive b. Inducible c.Negatively controlled d. Repressible 2. What is the role of the lacZ gene product, the enzyme -galactosidase? a. It facilitates the entry of lactose into the bacterial cell. b. It removes the toxic by-products of lactose digestion from the bacterial cell. c.It converts lactose to glucose and galactose. d. It converts simple sugars to lactose. 3. What is the effect on transcription of the structural and regulatory genes of the lac operon when lactose is present in the environment? a. Transcription of the structural genes occurs. b. The genes are transcribed for only a single generation and then are shut off. c.Transcription does not occur. d. Lactose represses the synthesis of the repressor. 4. Which molecule is the true inducer of the lactose operon? a. Dextrose b. Glucose c.Allolactose d. Galactose 5. True or false? A mutation in the I gene directly affects the promoter of the lac operon. 6. Which of the following statements describes what occurs in a bacterial cell as a consequence of high glucose concentrations? a. There is no effect. b. When glucose is present, the cell will convert it to lactose and use that as the carbon source. c.When glucose is present, the levels of cyclic AMP are low, and so the lac operon genes are transcribed d. When glucose is present, the levels of cAMP are low. CAP alone will not bind to the CAP binding site, and so the structural genes are not transcribed. 7. When a bacterial cell is present in an environment where both lactose and glucose are present, the glucose will be metabolized first and the lactose will be used when the stores of glucose have been depleted. How does a bacterial cell recognize the fact that glucose is present and turn off transcription of the lac genes even when lactose is present? a. A CAP-cAMP complex is required for transcription, and its level is low when glucose is present. b. The CAP binding site is activated. c.Glucose is a repressor molecule. d. The lac promoter binds glucose and shuts down the lac operon. 8. Which of the following statements best describes the trp operon? a. It is repressible and under negative control. b. It is inducible and under negative control....
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