Mod 6 Ch. 14 Flashcards Preview

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Flashcards in Mod 6 Ch. 14 Deck (25):

A repressor is a ___ that ___ transcription.

Regulatory protein, inhibits


Which of the following conditions would cause transcription to be activated?

A repressor plus an inducer


What is an operon?

A group of genes under the control of a single promoter


The binding of ___ to the lac repressor causes the lac repressor to ___ to the operator site, thereby ___ transcription.

Allalactose, not bind, increasing


On its chromosome, an E. coli cell is lacl- lacZ+ lacY+ lacA+. It has an F' factor that is lacl+ lacZ+ lacY+ lacA+. What is the expected level of expression of the lac operon genes (lacZ+ lacY+ lacA+) in the absence of lactose?

Neither lac operon would be expressed


How does exposing an E. coli cell to glucose affect the regulation of the lac operon via CAP?

cAMP does not bind to CAP and transcription is decreased


When tryptophan binds to the trp repressor, this causes the trp repressor to ___ to the trp operator and ___ transcription.

Bind, inhibit


During attenuation, when tryptophan levels are high, the ___ step-loop forms and transcription ___ the trpL gene.

3-4, ends just past


Operons involved with the biosynthesis of molecules, such as amino acids, are most likely to be regulated in which of the following manners?

The product of the biosynthetic pathway represses transcription


Translation can be regulated by..

- translational repressors
- antisense RNA


An example of a posttranslational covalent modification that may regulate protein function is ..



For a riboswitch that controls transcription, the binding of a small molecule such as TPP controls whether the RNA..

Has an antiterminator or terminator stem-loop


Common points where regulation of gene expression occurs in bacteria.

What is an advantage of gene regulation?

Gene regulation is more efficient. A cell does not waste energy making RNAs and proteins it does not need.


Binding sites on a genetic regulatory protein.

Which of these are genetic regulatory proteins and which are small effector molecules?

Activators and repressors are regulatory proteins. Inducers, corepressors, and inhibitors are small effector molecules.


Organization of the lac operon and other genes involved with lactose metabolism in E. coli.

Which genes are under the control of the lac promoter?

lacZ, lacY, and lacA genes


The cycle of lac operon induction and repression.

Under what conditions is the lac repressor bound to the lac operon?

When it is not exposed to lactose- when allalactose is not bound to the repressor


Why is it beneficial for the bacterium to regulate the lac operon with both a repressor protein and an activator protein?

The repressor protein allows the cell to avoid turning on the operon in the absence of lactose. The activator protein allows the cell to choose between glucose and lactose.


The identification of three lac operator sites.

Which data provide the strongest evidence that O1 is not the only operator site?

The data in which O2 and O3 are deleted indicate that O1, by itself, is not very strong in repressing the lac operon


How does tryptophan affect the function of the trp repressor?

Tryptophan acts as a corepressor that causes the trp repressor to bind to the trp operon and repress transcription


Sequence of the trpL mRNA produced during attenuation.

What type of bonding interaction causes the stem-loops to form?

Hydrogen bonding between complementary sequences


Explain how the presence of tryptophan favors the formation of the 3-4 stem-loop.

Causes the trpL gene to be translated to its stop codon. This blocks both regions 1 and 2, which allows a 3-4 stem-loop to form. The 3-4 stem-loop causes transcriptional termination.


How does micF antisense RNA affect the translation of ompF mRNA?

The micF antisense RNA binds to the ompF mRNA and inhibits its translation


Why is feedback inhibition an advantage to the bacterium?

It prevents a bacterium from overproducing the product of a metabolic pathway


Which RNA conformation favors transcription?

The RNA conformation with an antiterminator stem-loop favors transcription


Which RNA conformation favors translation?

The RNA conformation with the Shine-Dalgarni antisequestor