Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome. 1) If she moves the promoter for the lac operon to the region between the beta galactosidase (lacZ) gene and the permease (lacY) gene, which of the following would be likely? A) RNA polymerase will no longer transcribe permease. B) The cell will continue to metabolize but more slowly. C) The operon will no longer be inducible. D) Beta galactosidase will not be produced. E) The three genes will be expressed normally. 2) The tryptophan operon in some bacteria is a repressible operon that is A) turned off whenever tryptophan is added to the growth medium. B) turned off only when glucose is present in the growth medium. C) permanently turned on. D) turned on only when tryptophan is present in the growth medium. E) turned on only when glucose is present in the growth medium. 3) What would be the result of a mutation that deactivates the regulatory gene of a repressible operon in an Escherichia coli cell? A) inactivation of RNA polymerase by alteration of its active site B) continuous transcription of the structural gene controlled by that regulator C) irreversible binding of the repressor to the operator D) complete inhibition of transcription of the structural gene controlled by that regulator E) continuous translation of the mRNA because of alteration of its structure 4) For a repressible operon to be transcribed, which of the following must occur? A) RNA polymerase and the active repressor must be present. B) A corepressor must be present. C) RNA polymerase must bind to the promoter, and the repressor must be inactive. D) RNA polymerase cannot be present, and the repressor must be inactive. 5) Gene expression can be blocked by small RNA molecules called siRNAs. What is this process called? A) RNA targeting B) RNA interference C) RNA disposal D) RNA blocking
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This is because the lac operon is inducible, meaning that it is only transcribed when lactose is present. The promoter mutation would prevent RNA polymerase from binding to the promoter and initiating transcription of the lacZ gene, which codes for Beta Show more…
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The lac operon consists of regulatory regions such as the promoter as well as the structural genes lacZ, lacY, and lacA, which code for proteins involved in lactose metabolism. What would be the outcome of a mutation in one of the structural genes of the lac operon? a. Mutation in structural genes will stop transcription. b. Mutated lacY will produce an abnormal $\beta$ galactosidase protein. c. Mutated lacA will produce a protein that will transfer an acetyl group to $\beta$ galactosidase. d. Transcription will continue but lactose will not be metabolized properly.
What would occur if the repressor of an inducible operon were mutated so it could not bind the operator? \begin{equation} \begin{array}{l}{\text { (A) irreversible binding of the repressor to the promoter }} \\ {\text { (B) reduced transcription of the operon's genes }} \\ {\text { (C) buildup of a substrate for the pathway controlled by the }} \\ {\text { operon }} \\ {\text { (D) continuous transcription of the operon's genes }}\end{array} \end{equation}
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