MASTERING CH. 18 – Flashcards
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Which of the following levels of gene expression control allows a cell to conserve the most resources?
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transcpitional control
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Which of the following levels of gene expression control allows a cell to respond most rapidly to a changing environment?
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post-translational control
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The operon model of the regulation of gene expression in bacteria was proposed by _____.
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jacob and monod
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Which of these is NOT a component of the lac operon?
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regulatory gene only
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Regulatory proteins bind to _____.
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the operator
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In the presence of a regulatory protein the lac operon is _____.
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not transcribed
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The lac repressor protein binds to the operator when it is ______.
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not bound to lactose
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Which of the following leads to the highest rate of lac operon transcription?
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high lactose levels and low glucose levels
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Allosteric regulation occurs when ______.
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a regulatory molecule binds to a protein to change its shape and activity
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An operon is ______.
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a set of bacterial genes that are regulated together and transcribed into a single RNA
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What is the role of lactose in regulating lac operon expression?
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it induces transcription by binding to the repressor and causing its release from the operator
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The product of the lacI gene is _____.
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the repressor
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There is a mutation in the repressor that results in a molecule known as a super-repressor because it represses the lac operon permanently. Which of these would characterize such a mutant?
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it cannot bind to the inducer
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Regarding regulation of the ara operon, what would be the effect of a mutation that removes the part of the AraC protein that binds to RNA Polymerase?
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transcription would not occur at high levels in either the presence or absence of arabinose
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Which of the following is the protein that positively regulates transcription of the ara operon?
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AraC
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When many genes of an organisms are globally regulated, those genes are considered as regulon genes. What is the common theme of such genetic regulation?
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genes of regulons are silenced by a common repressor
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An E. coli cell without a functional lacI gene is expected to _____.
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always produce B-galactosidase
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What is the pattern of expression of β-galactosidase in lacI— cells and why?
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constitutive expression, because there is no repressor
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Predict what would happen if the lac repressor protein were altered so it could not bind inducer.
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the repressor would always be bound to DNA
