BIO EXAM 4 (ch 18) – Flashcards

Which of the following levels of gene expression control allows a cell to respond most rapidly to a changing environment? A) transcriptional control B) post-translational control C) pre-RNA splicing control D) translational control

At which of the following stages does transcriptional control occur? a b c DNA ——> mRNA ——> protein ——> activated protein

Imagine that you want to isolate mutant cells that are deficient in the enzymes required to synthesize tryptophan. You decide to use a replica plating protocol similar to Figure 18.3. What should the composition of the growth media in the master and replica plates be?

What is the pattern of expression of β-galactosidase in lacI— cells and why?

The lac repressor protein binds to the operator when it is ______.

The operon model of the regulation of gene expression in bacteria was proposed by _____.

Which of these is NOT a component of the lac operon? A) lactose-utilization genes only B) promoter only C) regulatory gene only D) operator only E) promoter and operator

Regulatory proteins bind to _____. A) the operator B) the lactose-utilization genes C) the regulatory gene D) RNA polymerase E) transcription factors

In the presence of a regulatory protein the lac operon is _____. A) transcribed B) not transcribed C) transcribed at a faster than usual rate D) is turned on E) either transcribed or not transcribed

________ inactivates the repressor protein so that the lactose-utilization genes can be transcribed.

RNA polymerase transcribes the genes of the?

A(n) ________ is a stretch of DNA consisting of an operator, a promoter, and genes for a related set of proteins, usually making up an entire metabolic pathway.

The ______ is/are arranged sequentially after the promoter.

A(n) ________ is a specific nucleotide sequence in DNA that binds RNA polymerase, positioning it to start transcribing RNA at the appropriate place.

A(n) _____ codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes.

Regulatory proteins often bind to the _________ to control expression of the operon.

AA(n) ________ is a protein that inhibits gene transcription. In bacteria, this protein binds to the DNA in or near the promoter.

A(n) ________ is a specific small molecule that binds to a bacterial repressor protein and changes its shape so that it cannot bind to an operator, thus switching an operon on.

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?

Which aspect of normal lac operon function is an example of post-translational control? A) Interaction of lactose with galactoside permease B) Control of repressor protein synthesis C) Binding of repressor to the operator D) Interaction of lactose with the repressor

A type of mutation in the lac operator known as lacOc prevents repressor binding to DNA and causes constitutive transcription of the lac operon. Which of the following secondary mutations might restore normal regulation to the operon in a mutant? A) a lacI mutation that produces a repressor than can recognize the mutated lacOc DNA sequence B) a promoter mutation that prevents it from being recognized by sigma C) a lacI mutation that decreases the ability of the repressor to bind the inducer D) an RNA polymerase mutation that allows it to bind to the promoter without using sigma

Colonies of what color are produced by cells with functioning copies of β-galactosidase?

Colonies of what color are produced by cells with mutations in the lacZ or in the lacY genes?

Suppose you analyze the protein-coding sequence of the lacZ and lacY genes of cells from the three mutant colonies and find that these sequences are wild type (normal). What other region of the lac operon might be altered to account for the mutant phenotype of these colonies?

Of the three modes of gene regulation shown in Figure 18.1, which is the most efficient in resource use?

What is the role of lactose in regulating lac operon expression?

An operon is ______

Which of the following leads to the highest rate of lac operon transcription? A) low lactose levels and low glucose levels B) low lactose levels and high glucose levels C) high lactose levels and low glucose levels D) intermediate levels of lactose and glucose E) high lactose levels and high glucose levels

Which of the following is the protein that positively regulates transcription of the ara operon? A) glucose B) arabinose C) the lac repressor D) AraC E) the ara operator

Allosteric regulation occurs when ______.

Using the car analogy for regulation of gene expression in which negative control is exerted by setting the parking brake and positive control is exerted by stepping on the gas pedal, which answer best defines a component of lac operon control? A) Operator=serves as part of the gas pedal B) Inducer (lactose)=steps on the gas pedal C) Inducer (lactose)=releases parking brake D) Repressor=releases the parking brake

Predict what would happen if the lac repressor protein were altered so it could not bind inducer.

If any of the following hypothetical drugs could be developed, which would be most effective in preventing cholera? A) a drug that increased the amount of the ToxR activator B) a drug that blocked the DNA-binding activity of the activator C) a drug that increased rates of translation in V. cholerae D) a drug that increased rates of transcription in V. cholerae

How does inducer exclusion control gene expression in the lac operon?

What is a tumor suppressor? A) a viral RNA that interacts with mRNA and blocks the translation B) a gene or protein that prevents cell containing tumor markers from division C) a gene or protein that blocks cell division forever D) a gene or protein that holds cell division in check unless conditions are right for the cell to divide

In eukaryotes, what allows only certain genes to be expressed in certain types of cells? A) the set of mediator proteins B) the set of basal transcription factors C) the set of regulatory transcription factors D) the set of histone and non-histone proteins

The lac operon undergoes negative control. When lactose is ______, the repressor protein is active, and transcription is turned off. When lactose is ______, the repressor protein is inactivated, and transcription is turned on.

In the presence of arabinose 1. AraC binds to... 2. AraC acts as... 3. Does transcription of the area operon occur? 4. Does arabinose metabolism occur?

In the absence of arabinose 1. AraC binds to... 2. AraC acts as... 3. Does transcription of the area operon occur? 4. Does arabinose metabolism occur?

If a mutation prevents arabinose from binding to AraC 1. AraC binds to... 2. AraC acts as... 3. Does transcription of the area operon occur? 4. Does arabinose metabolism occur?

If arabinose is present but a mutation is araD enzyme renders it non-functional 1. AraC binds to... 2. AraC acts as... 3. Does transcription of the area operon occur? 4. Does arabinose metabolism occur?