Chapter 14

How many binding sites are there in the lac operon for the lac repressor?

3

Transcription of the lac operon results in the production of how many different mRNA transcripts?

1

Bacteria use riboswitches extensively; about ___ of bacterial genes are regulated this way.

4%

Put the following in order: 1-CAP site, 2-lacZ, 3-lacY, 4-lac operon, 5-lacI, 6-i promoter, 7-lacO, 8-lac promoter, 9-lacA

6,9,1,8,7,4,2,3,9

How can antisense RNA inhibit translation?

An antisense RNA binds to a transcript and inhibits translation.

T/F: An inducer binds to an activator protein and inhibits transcription.

False

T/F: An inhibitor regulates an inducible gene.

False

T/F: The CAP protein is an activator that binds to the operator.

False

T/F: The structural proteins encoded by the lac operon are involved in lactose synthesis.

False

T/F: When both glucose and lactose are absent, transcription of the lac operon occurs.

False

How is the lac operon regulated?

It is inducible under negative and positive control

Which combination of two operator sites have the lowest amount of repression?

O2 and O3

Determine if it describes regulation at the transcription, translation or post-translation level: A protein is covalently modified.

Posttranslation

The absence of lactose results in the lac repressor protein ____.

binding to the DNA

One form of gene expression control found frequently in prokaryotes involves a ___, which occurs when an RNA can exist in two different secondary conformations.

riboswitch

One conformation of the RNA requires a small molecule binding which stabilizes the ____ structure.

secondary

The RNA forms stem loops as it is being...

transcribed

The trp operon is also regulated by ___ attenuation.

transcription

When both glucose and lactose are present

transcription of the lactose operon is turned off.

Riboswitches can regulate transcription, ___ , and RNA stability.

translation

Translation of mRNA transcribed from the trp operon can be regulated by formation of a secondary structure within the mRNA. The mRNA that forms this secondary structure is transcribed from which gene in the trp operon?

trpL

Determine if it describes regulation at the transcription, translation or post-translation level: The product of a metabolic pathway inhibits the first enzyme in a pathway.

Posttranslation

If a cell has a mutation in the lacY gene that produces a non-functional product, how is regulation of the lac operon affected?

The lac operon cannot be induced, because lactose cannot enter the cell. (lacY gene encodes lactose pernease which is required for active transport of lactose into the cytoplasm of the bacterium)

How would the interpretation of the Jacob, Monod, and Pardee experimental results change if lacO was mutated instead of lacI?

The lac operon has constitutive expression and O has a cis-effect

Determine if it describes regulation at the transcription, translation or post-translation level: A transcription terminator forms in the RNA.

Transcription

Determine if it describes regulation at the transcription, translation or post-translation level: Genetic regulatory proteins bind to the DNA.

Transcription

In Bacilus subtilis, a riboswitch controls the ___ of the thi operon involved in thiamin pyrophosphate synthesis.

Transcription

Determine if it describes regulation at the transcription, translation or post-translation level:Antisense RNA binds to the mRNA.

Translation

Determine if it describes regulation at the transcription, translation or post-translation level:Repressor proteins bind to an mRNA and prevent ribosome binding.

Translation

Determine if it describes regulation at the transcription, translation or post-translation level:Riboswitches produce an RNA conformation that prevents ribosome binding.

Translation

T/F: CAP binding causes the DNA to bend facilitating RNA polymerase binding.

True

T/F: In the absence of glucose and presence of lactose, allolactose combines with the repressor and allows RNA polymerase to proceed with transcription.

True

T/F: Polycistronic mRNA is transcribed from the lac operon when lactose is present in the cell.

True

T/F: The LacI gene makes a repressor protein.

True

T/F: The lac repressor protein is active in the absence of lactose within the cell.

True

T/F: The presence of a small effector molecule may inhibit transcription.

True

T/F: The product of LacI is an allosteric protein that can undergo a conformational change when allolactose binds to it.

True

Attenuation of the trp operon requires which conditions to be met?

Tryptophan levels must be high, and regions 3 and 4 must pair.

The lac repressor is inactivated by binding to which of the following?

allolactose

The lac repressor

binds to the operator and prevents transcription of the lactose operon.

When glucose is present ...

cyclic AMP is low, CAP does not bind to the activator binding site, and transcription of the lactose operon is turned off.

The repressor is bound to the operator when tryptophan levels are ...

high

he attenuator is similar to rho ___ termination.

independent

Which of the following is not part of the lac operon?

lacI

The lac repressor binds to what site within the lac operon?

lacO

Which gene is responsible for producing the protein that converts lactose to allolactose?

lacZ

The cAMP-CAP binding site is between operators O1 and O3. When cAMP-CAP is bound it facilitates binding of the repressor. Under what conditions would this occur?

low glucose and low lactose

What combination of glucose and lactose would result in high levels of gene transcription from the lac operon?

low glucose, high lactose

Which of the following would not be considered a reversible posttranslational modification?

proteolytic processing

The trpR gene encodes a ...

repressor