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gene expression

gene expression - Clicker Question 141 Constitutive genes...

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Unformatted text preview: 8/28/08 Clicker Question 141 Constitutive genes A.are expressed continuously. B.are expressed unless repressed by a regulator molecule. C.are expressed in conjunction with other genes. D.are not expressed unless induced by a regulator molecule. E.are genes for products that function in specialized cell types. Clicker Question 142 A(n) __________ operon is normally turned on, and it is turned off by a(n) _________. A.inducible; activator B.inducible; repressor C.repressible; activator D.repressible; repressor 1 8/28/08 Clicker Question 143 To activate the transcription of permease (and the whole lac operon) lactose needs to be present in the cell. How can lactose get in the cell when the permease gene is not activated? A.The repressed lac operon is never completely repressed. B. There is a second permease in the genome that initially transports lactose. C.Lactose freely moves across the plasma membrane. D.Though the lac operon has been studied for many years, this mystery is unsolved. Clicker Question 144 A mutation in the P region of the lac operon would most likely result in A. constitutive expression of lac, as the repressor cannot bind. B. constitutive expression of lac, as lactose cannot bind. C. reduced expression of lac. D. production of nonfunctional galactosidase. E. no change in the expression of lac. 2 8/28/08 Clicker Question 145 When trptophan concentrations are high, what happens? A.Tryptophan binds the repressor so that it can repress trp operon transcription. B.Attenuation causes premature termination of transcription. C.The tryptophan synthesis genes are not transcribed. D.all of the above Negative Inducible Operon Substrate makes the represssor inactive. 3 8/28/08 Negative Repressible Operon Product makes the represssor active. Positive Inducible Operon Substrate makes the activator active. 4 8/28/08 Positive Repressible Operon Product makes the activator inactive. 5 8/28/08 6 ...
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