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
