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MB Chapter 17
Terms in this set (18)
Of the three modes of gene regulation shown in the figure, which is the fastest in response time?
post-translational control. Because this mode involves modification of an already synthesized protein, it is the fastest in terms of regulating the activity of the gene product.
Of the three modes of gene regulation shown in the figure, which is the most efficient in resource use?
transcriptional control. Transcriptional control can stop gene expression at the earliest possible step, saving the most energy and materials for the cell.
At which of the following stages does transcriptional control occur?
DNA -a-> mRNA -b-> protein -c-> activated protein
The operon model of the regulation of gene expression in bacteria was proposed by _____.
Jacob and Monod. In 1961 Jacob and Monod proposed the operon model of gene regulation.
Which of these is NOT a component of the lac operon?
lactose-utilization genes only
regulatory gene only
promoter and operator
regulatory gene only. The regulatory gene, while not a part of the operon, plays a role in regulating the expression of the genes of the operon.
Regulatory proteins bind to _____.
the operator. Transcription is inhibited when a regulatory protein binds to the lac operon operator.
In the presence of a regulatory protein the lac operon is _____.
not transcribed. The regulatory protein of the lac operon is a repressor.
What is the function of lactose in the lac operon?
Lactose inactivates the repressor protein so that the lactose-utilization genes can be transcribed.
What is the function of RNA polymerase in the lac operon?
RNA polymerase transcribes the genes of the lac operon.
What is the relationship between the regulatory gene and the lac operon?
The regulatory gene is not a part of the operon.
What is the role of lactose in regulating lac operon expression?
It induces transcription by binding to the repressor and removing it from the operator.
An operon is _____.
a set of bacterial genes that are regulated together and transcribed into a single RNA
Allosteric regulation occurs whenever _____.
a regulatory molecule binds to a protein to change its shape and activity
How would positive and negative control work together to control the lac operon in the absence of both glucose and lactose (i.e., what would the shown figure look like if both glucose and lactose were LOW)?
CAP bound to CAP site; repressor bound to operator; infrequent transcription. Although cAMP levels would be high and the binding of the CAP-cAMP complex to the CAP site would encourage tight binding of RNA polymerase to the promoter, absence of lactose means the repressor would also be bound to the operator, blocking transcription. (It would be wasteful for E. coli to transcribe lac operon genes frequently in the absence of lactose.)
Which of the following leads to the highest rate of lac operon transcription?
high lactose levels and low glucose levels
Which of the following works in the positive regulation of the lac operon?
the CAP protein
the lac operator
the lac repressor
the CAP protein
How would gene expression in your gut-dwelling bacteria change after you drink a glass of milk?
lac operon gene expression would be induced. The lactose in milk would induce lac operon transcription. (Note that transcription would be optimal only if glucose levels in your gut were low.)
Using the car analogy for regulation of gene expression in which negative control is exerted by setting the parking brake and positive control occurs by stepping on the gas pedal, which answer best defines a component of lac operon control?
CAP binding site = part of gas pedal. When the CAP protein (as the CAP-cAMP complex) binds to the CAP binding site, transcription is triggered because CAP interacts with RNA polymerase in a way that allows transcription to begin more frequently.
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