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BIOL 3025

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The lac operon is expressed when
A) glucose is high and lactose is absent.
B) glucose is low and lactose is absent.
C) glucose is low, regardless of the presence or absence of lactose.
D) glucose is high and lactose is present.
E) glucose is low and lactose is present.
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Terms in this set (92)
The lac operon is expressed when
A) glucose is high and lactose is absent.
B) glucose is low and lactose is absent.
C) glucose is low, regardless of the presence or absence of lactose.
D) glucose is high and lactose is present.
E) glucose is low and lactose is present.
E
When in a complex with ________, the CAP protein binds to the CAP site and ________ the expression of the lac operon.
A) glucose ; switches on
B) lactose ; switches on
C) cAMP ; switches on
D) cAMP ; switches off
E) glucose ; switches off
C
In the absence of lactose, the lac repressor is
A) active and can bind to the operator.
B) inactive and can bind to the operator.
C) active and cannot bind to the operator.
D) inactive and cannot bind to the operator.
E) inactive and cannot bind to the promoter.
A
Which region associated with the lac operon is not involved in the binding of RNA polymerase?
A) lacO
B) lacZ Correct
C) CAP binding site
B
How does glucose effect the lac operon?
A) When glucose levels are high, glucose binds to and deactivates the repressor, preventing it from binding to the DNA.
B) When glucose levels are low, it stimulates the production of cAMP, which binds to and deactivates the repressor, preventing it from binding to the DNA.
C) When glucose levels are low, glucose binds to and activates the repressor, causing it to associate with the DNA.
D) When glucose levels are high, it stimulates the production of cAMP, which binds to and deactivates the CAP protein, preventing it from binding to the DNA.
E) When glucose levels are low, it stimulates the production of cAMP, which binds to and activates the CAP protein, allowing it to bind to the DNA.
NOT A B C E
NOT A B D
Why does the concentration of glucose have an effect on the transcription of the lac operon?
A) Glucose is an important cell signaling molecule.
B) All of these are true
C) The lac operon functions to metabolize glucose, lactose, and other small sugars.
D) Glucose is the preferred sugar for the bacteria. If it is present, lactose metabolism is suppressed.
E) Glucose is a precursor of lactose.
D
DNA is associated with proteins to form _____.
chromatin
A _____ is composed of DNA wrapped around an octamer of histone proteins.
nucleosome
An activator can increase transcription by attracting a _____ to the region.
histone acetyltransferase
Addition of (-COCH₃) groups to histone amino terminal tails results in a/an _____ in gene expression.
increase
Removal of acetyl groups from histones results in a/an _____ in gene expression.
decrease
How is it possible for a single gene to encode more than one polypeptide?
A) It is not possible; this violates the "one gene - one enzyme" hypothesis.
B) Introns can be removed from pre-mRNA in different combinations.
C) mRNA bases can be rearranged in a modular fashion.
D) A single transcription factor can regulate many genes.
E) The exons in DNA can undergo a shuffling process during S phase.
B
How could an activator influence gene expression at a promoter far away from the place that it binds DNA?
A) Histone proteins are modified to create a closed conformation.
B) Ribosomes are recruited to the promoter by the activator.
C) The activator methylates the DNA and this causes long-distance activation.
D) The activator directly binds to RNA polymerase, which then skips over a large region of DNA to start transcription.
E) A Mediator protein is stimulated by the bound activator, and then the Mediator stimulates transcription.
E
Distinguish between the characteristics associated with each of the four types of gene regulation.

Transcriptional

A) The correct removal of introns of a pre-mRNA is prevented.
B) The rate of degradation of a protein is increased
C) Stability of an mRNA is regulated.
D) An activator binds to an enhancer.
E) A repressor binds near a promoter
F) A phosphate group is added to a protein, making it inactive.
G) The ability of an mRNA to bind to ribosomes is changed.
H) Export of an mRNA to the cytoplasm is blocked.
I) The 5' end of an mRNA forms a shape that blocks translation.
D E
Distinguish between the characteristics associated with each of the four types of gene regulation.

Post-transcriptional

A) The correct removal of introns of a pre-mRNA is prevented.
B) The rate of degradation of a protein is increased
C) Stability of an mRNA is regulated.
D) An activator binds to an enhancer.
E) A repressor binds near a promoter
F) A phosphate group is added to a protein, making it inactive.
G) The ability of an mRNA to bind to ribosomes is changed.
H) Export of an mRNA to the cytoplasm is blocked.
I) The 5' end of an mRNA forms a shape that blocks translation.
A C H