Reflect and then discuss with your peers the following scenario 2... You are a scientist tasked with engineering a strain of E. coli in which the lac operon is completely repressed, even when lactose is present. Which of the following genes or regulatory regions would be logical targets for a mutation to achieve this goal? (Check all that lacl Promoter Region Operator region lacZ /acy Reguletory gene
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The lac operon consists of several key elements: the lacZ gene (which encodes β-galactosidase), the lacY gene (which encodes lactose permease), the lacA gene (which encodes thiogalactoside transacetylase), the promoter region (where RNA polymerase binds to Show more…
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Adi S.
1. The lac operon in E. coli comprises three structural genes, lac Z, lacY, and lacA. It is regulated by both positive and negative mechanisms, involving binding of both a repressor protein and the catabolite activator protein (CAP). Transcription of the operon yields a polycistronic mRNA encoding the three enzymes. Under the following nutritional conditions, indicate whether or not the repressor and the CAP are bound (yes/no), and if bound, to which region(s) of the operon (write the corresponding letter and symbol – e.g., Z+ if bound to the lac Z gene). Also indicate whether or not a messenger RNA is made by indicating whether the expected amount of product is: none, low, medium, high. a. When lactose and glucose are absent: |_p_| i+ |_p+|_o+| z+ | y+ | a+ | Repressor bound? ________ to: ________ CAP bound? ________ to: ________ Expected amount of product: ________ b. When lactose is present and glucose is absent: |_p_| i+ |_p+|_o+| z+ | y+ | a+ | Repressor bound? ________ to: ________ CAP bound? ________ to: ________ Expected amount of product: ________ c. When both lactose and glucose are present: |_p_| i+ |_p+|_o+| z+ | y+ | a+ | Repressor bound? ________ to: ________ CAP bound? ________ to: ________ Expected amount of product: ________
Farhan A.
1. To inhibit the transcription of operon genes, the lacI gene product binds to __________. a. the inducer b. the promoter c. the operator d. the lacZ gene e. the repressor 2. A DNA mutation (resulting in a lack of function) in which of the following locations would lead to constitutive expression of the lac operon genes? (Select all that apply.) a. the lacI promoter b. the lac operon promoter c. the lac operon operator d. the lacZ gene e. the lacI gene 3. Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the lacI (repressor) gene, along with its promoter, to a position at some several thousand base pairs away from its normal position, we would expect that: a. the repressor protein will no longer be made. b. the repressor protein will no longer bind to the operator in absence of lactose. c. the repressor protein can no longer bind to the inducer if present. d. the lac operon will be expressed continuously. e. there will be no difference in repressor gene or lac operon function. 4. Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. If she moves the operator to the far end of the operon, downstream of the transacetylase (lacA) gene, which of the following would likely occur when the cell is exposed to lactose? a. The inducer will not bind to the repressor. b. The repressor will not bind to the operator. c. The operon will not be transcribed. d. The lacZ, lacY, and lacA genes will be transcribed continuously. e. The repressor protein will not be produced.
Sri K.
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