Deck 14: Gene Regulation

Question 1

Bacterial enzymes that are part of a rarely used catabolic pathway are usually organized into a(n) __________.

A) inducible operon
B) repressible operon
C) inducible zinc finger
D) repressible leucine zipper
E) inducible catabolon

Answer 1

A

Question 2

An activator protein would have which of the following effects on an operon with a positive control mechanism?

A) stimulate transcription
B) turn off transcription
C) stimulate transcription when a coactivator is bound to the allosteric site
D) inhibit transcription when a coactivator is bound to the allosteric site
E) no response

Answer 2

C

Question 3

Genes that encode proteins that are always needed are called:

A) repressible genes.
B) promoter genes.
C) constitutive genes.
D) inducible genes.
E) operons.

Answer 3

C

Question 4

How does the lactose repressor block transcription of the lactose operon?

A) by "turning off" the appropriate genes in the intron
B) by regulating the activity of the enzymes that the operon codes for
C) by binding allosterically to the appropriate genes
D) by slowing the uptake of lactose into the cell
E) by binding to the operator

Question 5

In the tryptophan operon, the repressor actively binds to the operator when:

A) tryptophan binds to an allosteric site on the repressor.
B) tryptophan levels are low.
C) lactose levels are low.
D) there is a great need for proteins.
E) allotryptophan levels are low.

Question 6

An inducible operon is usually controlled by:

A) an inducer molecule that keeps it in the "off" state.
B) an active repressor that keeps it in the "off" state.
C) being active at all times.
D) allolactose.
E) being turned "off," usually by the end product of the pathway.

Question 7

cAMP levels decrease when __________.This results in __________ of CAP.

A) lactose levels increase; activation
B) lactose levels decrease; inhibition
C) glucose levels increase; inhibition
D) glucose levels decrease; activation
E) glucose levels decrease; inhibition

Question 8

Lactose induces the transcription of the lactose operon by:

A) binding to the allosteric site of the repressor after being converted to allolactose.
B) stimulating lactose metabolism in the cell.
C) binding to the glucose operon, making it inoperable.
D) binding to the allosteric site of RNA polymerase.
E) inhibiting the activity of CAP.

Question 9

The inducer of the lactose operon in E.coli is:

A) CAP.
B) AMP.
C) allolactose.
D) glucose.
E) galactose.

Question 10

The focus of gene regulation in multicellular organisms is on:

A) operons.
B) the specificity of products in different tissues.
C) economizing resources at all levels.
D) rapid turnover of RNA molecules.
E) controlling the transcription of genes involved in resource use

Question 11

The molecular switch that controls gene expression is known as:

A) the operon.
B) controller.
C) the operator.
D) repressor.
E) inducer.

Question 12

Repressible genes are usually actively transcribed when:

A) repressor molecules bind to the promoter.
B) the supply of the end product formed by the enzymes encoded by these genes is low.
C) tryptophan accumulates in the cell.
D) quantities of precursor materials are high.
E) there is no other substrate that can be used by the cell.

Question 13

Catabolite activator protein:

A) increases the affinity of the promoter region for RNA polymerase.
B) decreases RNA polymerase activity.
C) becomes nonfunctional when it binds to AMP.
D) binds and activates RNA polymerase.
E) blocks RNA polymerase access to the DNA template.

Question 14

Inducible genes are usually actively transcribed when:

A) the molecule degraded by the enzyme(s) is present in the cell.
B) repressor molecules bind to the promoter.
C) lactose is absent from the cell.
D) quantities of precursor materials are low.
E) there is no other substrate that can be used by the cell.

Question 15

The gene that codes for the repressor protein of the E.coli lactose operon is:

A) located between the operator and the promoter.
B) downstream from the promoter region.
C) downstream from the operator.
D) constitutive.
E) turned off most of the time.

Question 16

A repressible operon is usually controlled by:

A) an inactive repressor that allows it to be in the "on" state.
B) the supply of the precursor product for the enzymes.
C) an inactive repressor that keeps it in the "off" state.
D) tryptophan.
E) being turned "on," usually by the end product of the pathway.

Question 17

Regulation of gene expression can NOT be accomplished by controlling:

A) the activity of a protein product.
B) the amount of mRNA that is available.
C) the rate of translation of mRNA.
D) the rate of mRNA degradation.
E) the rate of DNA replication

Question 18

Bacteria rarely regulate gene products through:

A) promoter sequences.
B) activator proteins.
C) repressor proteins.
D) protein degradation.
E) operons.

Question 19

The researchers who first discovered the mechanism of control of a bacterial gene were:

A) Hershey and Chase.
B) Griffith and Avery.
C) Watson and Crick.
D) Jacob and Monod.
E) McClintock and Morgan.

Question 20

The operator of the lactose operon in E.coli is located:

A) between the promoter and the TATA box.
B) upstream of the promoter.
C) between the promoter and the structural genes.
D) among the structural genes.
E) anywhere on the chromosome.

Question 21

The role of CAP in the lac operon is:

A) repression of RNA polymerase binding to the promoter.
B) negative control of the lac operon.
C) enhancement of RNA polymerase binding to the promoter.
D) to inactivate the repressor by binding to its allosteric site.
E) the activation of allolactose binding to the repressor protein.

Question 22

Figure 14-1
Use the figure to answer the corresponding question(s).
The scenario in the accompanying figure reflects conditions of:

A) low levels of lactose.
B) high levels of lactose.
C) low levels of glucose.
D) high levels of glucose.
E) high levels of arabinose

Question 23

A new operon is discovered in a bacterium.The control of this operon is affected by a protein that is made by another gene, and is made in an active form that binds to the DNA near the operon to prevent transcription.This is an example of __________ control.

A) positive
B) negative
C) activational
D) repressing
E) inducing

Question 24

Feedback inhibition of the first enzyme of a pathway by the end product of the pathway is an example of:

A) translational control.
B) posttranslational control.
C) transcriptional control.
D) inhibiting control.
E) repression.

Question 25

Temporal gene regulation refers to which of the following circumstances?

A) Certain genes are induced only at a particular point in the life cycle.
B) Certain genes are induced only in specific tissues.
C) Heat-shock genes are induced during periods of temperature stress.
D) "Housekeeping" genes are induced in response to a viral infection.
E) Molecular chaperones are synthesized after heavy-metal ingestion.

Question 26

A repressor protein would have which of the following effects on repressible genes with a negative control mechanism?

A) stimulate transcription in the presence of a corepressor
B) turn off transcription in the presence of an inducer
C) stimulate transcription in the presence of a coactivator
D) turn off transcription in the presence of a corepressor
E) no response

Question 27

In female mammals, most of the inactive X chromosome has become:

A) associated with histones.
B) active X factor.
C) euchromatin.
D) replicated.
E) heterochromatin.

Question 28

Translational controls regulate:

A) the activity of a protein end-product that is produced.
B) the rate at which an mRNA molecule is translated.
C) the rate at which an mRNA molecule is synthesized.
D) the uptake of nucleic acids into the cell.
E) the attachment of phosphate groups to polypeptides.

Question 29

Feedback inhibition is:

A) transcriptional control.
B) transcriptional control.
C) a mechanism affecting events after translation.
D) a repressible system.
E) constitiutive control

Question 30

Genes in euchromatic regions are:

A) inhibited.
B) duplicated
C) actively being transcribed.
D) repressed.
E) unregulated.

Question 31

Densely staining regions of highly compacted chromatin that are generally not transcribed are:

A) heterochromatin.
B) homochromatin.
C) histone-dependent chromatin.
D) primary chromatin.
E) heterochromatinization

Question 32

In the lac operon, cAMP binds to:

A) DNA.
B) the repressor gene.
C) the operator gene.
D) the repressor protein.
E) catabolite activator protein.

Question 33

Which of the following statements concerning gene regulation in eukaryotes is FALSE?

A) The organization of tissues and organs is regulated mainly via transcription.
B) Some eukaryotic genes are constitutive.
C) Eukaryotic genes do not usually form operon-like clusters.
D) "Housekeeping" enzymes are expressed at all times.
E) Eukaryotic cells lack inducible genes.

Question 34

Translational controls of protein levels in bacteria are governed by:

A) the rate at which small and large subunits of ribosomes assemble.
B) the rate at which the cap and tail of pre mRNA are removed.
C) the rate at which ribosomes attach to mRNA molecules.
D) the concentration of proteins in the cytoplasm.
E) the rate at which sugars are incorporated into the cell.

Question 35

Which of the following statements about the regulation of gene expression in bacteria is false?

A) Genes can be turned on and off as environmental conditions change.
B) Constitutive genes producing enzymes that are more stable are transcribed at a slower rate.
C) Most gene regulation in bacteria occurs at the level of translation.
D) Constitutive genes encoding proteins required in large amounts are transcribed more rapidly than genes for proteins required in smaller amounts.
E) Constitutive genes with "strong" promoters bind RNA polymerase more frequently than genes with "weak" promoters.

Question 36

Figure 14-1
Use the figure to answer the corresponding question(s).
The promoter in Figure 14-1 is labeled __________.

A) 6
B) 3
C) 1
D) 2
E) 7

Question 37

Bacterial gene regulation occurs mainly at the __________ level.

A) translational
B) transcriptional
C) posttranscriptional
D) feedback inhibition
E) posttranslational

Question 38

DNA sequences that are methylated by a cell are usually genes that:

A) have been replicated
B) are actively expressed.
C) are inactive.
D) are constitutive.
E) are repressed.

Question 39

Figure 14-1
Use the figure to answer the corresponding question(s).
Refer to Figure 14-1.The area of the tryptophan operon labeled 3 is the:

A) promoter.
B) repressor gene.
C) ribosome.
D) RNA polymerase.
E) operator

Question 40

Figure 14-1
Use the figure to answer the corresponding question(s).
Refer to Figure 14-1.The structure labeled 7 in the figure of the tryptophan operon is:

A) an active repressor protein.
B) an inactive repressor protein.
C) an active RNA polymerase.
D) an inactive RNA polymerase.
E) a ribosome.

Question 41

Enzymes that alter another protein or enzyme's activity by attaching a phosphate group are called:

A) kinases.
B) phosphatases.
C) phospators.
D) transcription factors.
E) coenzymes.

Question 42

In an operon, the switch that controls mRNA synthesis is the promotor, which is a sequence of bases upstream from the first structural gene.
__________________

Question 43

Proteolytic processing of eukaryotic proteins involves:

A) removal of a portion of the polypeptide chain from an inactive precursor of the protein.
B) the addition of one or more functional groups to a precursor protein.
C) the removal of one or more functional groups from a precursor protein.
D) removal of histones.
E) removing the cap and tail of a newly synthesized protein.

Question 44

Which of the following types of processing does eukaryotic mRNA NOT undergo before it becomes functional?

A) splicing
B) capping
C) polyadenylation
D) removal of introns
E) protein proteolysis

Question 45

A cell may meet the need for large quantities of a specific protein by all of the following EXCEPT :

A) continuously synthesizing the mRNA molecule that specifies that protein.
B) increasing the half-life of the mRNA that specifies the protein.
C) having multiple copies of the gene that codes for that protein.
D) amplifying protein genes by DNA replication
E) inhibition of DNA synthesis

Question 46

In eukaryotes, some DNA sequences act as introns in some cells and as exons in other cells.This is an example of __________.

A) gene repression
B) mRNA splicing
C) gene amplification
D) differential mRNA processing
E) gene processing

Question 47

Increasing the stability of a particular mRNA __________ the expression of that gene.

A) increases
B) does not affect
C) eliminates
D) decreases
E) silencers

Question 48

Which of the following statements concerning leucine zipper proteins is FALSE?

A) They are transcription factors.
B) They contain loops held together by zinc ions.
C) They form homodimers.
D) They form heterodimers.
E) They contain DNA-binding domains.

Question 49

The rate of eukaryotic transcription after initiation is affected by:

A) upstream promoter elements.
B) groups of genes arranged into operons.
C) the action of catabolite activator proteins.
D) how fast caps and tails can be added to pre-mRNA.
E) enhancers.

Question 50

Some eukaryotic DNA sequences act as introns in the cells of some tissues and exons in the cells of other tissues.This allows:

A) prevention of harmful mutation.
B) regulation of the rate of transcription.
C) formation of different types of closely related proteins.
D) regulation of the rate of translation.
E) repression of DNA replication.

Question 51

Upstream promoter elements in eukaryotes are:

A) nucleotide sequences that act as binding sites for RNA polymerase.
B) nucleotide sequences that regulate the efficiency of transcription initiation.
C) nucleotide sequences that contain the TATA box.
D) proteins that enhance RNA polymerase binding to the promoter.
E) proteins that inhibit RNA polymerase binding to the promoter.

Question 52

Constitutive genes code for proteins that are needed for survival .
__________________

Question 53

Explain the respective advantages associated with operons being inducible (e.g., the lactose operon) or repressible (e.g., the tryptophan operon).

Question 54

Gene amplification involves:

A) increasing the affinity of a gene to DNA polymerase.
B) extra replication of genes that specify a certain gene product only in cells needing this product.
C) improving the accuracy by which a gene is copied to produce an mRNA molecule.
D) enhancing the activity of RNA polymerase.
E) increasing the size of the gene that encodes a needed protein.

Question 55

A TATA box is seen in __________ cells and is the site where __________.

A) bacterial; RNA polymerase binds
B) eukaryotic; DNA ligase cleaves introns
C) eukaryotic; RNA polymerase binds
D) both bacterial and eukaryotic; transcription factors bind
E) bacterial; a repressor protein binds

Question 56

Identify two ways in which posttranscriptional gene regulation occurs in eukaryotes and briefly explain each.

Question 57

Define operons as they occur in bacterial cells.

Question 58

DNA sequences called __________ increase the rate of RNA synthesis after initiation of transcription.

A) promoters
B) TATA boxes
C) UPEs
D) enhancers
E) regulators

Question 59

Eukaryotic transcription factors:

A) are always simpler than bacterial regulators.
B) may be activators or repressors of transcription.
C) are inducers.
D) are corepressors.
E) are also known as enhancers.

Question 60

Eukaryotic enhancers are capable of which of the following EXCEPT ?

A) regulating a gene even if they are cut out of the DNA and reinserted inverted
B) regulating a gene from very long distances
C) interacting with proteins that regulate transcription
D) increasing the rate of RNA synthesis after initiation
E) decrease the rate of transcription

Question 61

Much gene expression in multicelluar organisms focuses on quantitative gene expression of the genes in various tissues.
__________________

Question 62

Genomic imprinting is an example of epigenetics.
__________________

Question 63

Eukaryotes have inducible genes that respond to environmental stimuli.
__________________

Question 64

DNA methylation is a form of transcriptional regulation by eukaryotes.
____________________

Question 65

Mutations in the TATA box increase the rate of transcription.
__________________

Question 66

MATCHING
Match the type of gene regulation with the process.
a.regulation of transcription
d.regulation of translation
b.regulation of mRNA processing
e.regulation of chromatin
c.regulation of mRNA transport
Exon/intron processing

Question 67

The leucine zipper has a unique structure compared to the other transcription factors because it is a dimer.
__________________

Question 68

MATCHING
Match the type of gene regulation with the process.
a.regulation of transcription
d.regulation of translation
b.regulation of mRNA processing
e.regulation of chromatin
c.regulation of mRNA transport
Controlling access to nuclear pores

Question 69

Why is it important that a few $\beta$ -galactosidase molecules be present in E.coli even if these cells have been growing on a lactose-free medium?

Question 70

Outline the various ways in which chromosomes can regulate how much of an enzyme is present at any given time within a eukaryotic cell.

Question 71

When the intracellular level of lactose drops, the repressor protein binds to the operator and shuts down translation.
__________________

Question 72

MATCHING
Match the type of gene regulation with the process.
a.regulation of transcription
d.regulation of translation
b.regulation of mRNA processing
e.regulation of chromatin
c.regulation of mRNA transport
Sketch the main elements of an inducible operon, such as the lactose operon, and explain the functions of the operator and promoter regions.

Question 73

MATCHING
Match the type of gene regulation with the process.
a.regulation of transcription
d.regulation of translation
b.regulation of mRNA processing
e.regulation of chromatin
c.regulation of mRNA transport
Promotor and enhancer elements in DNA

Question 74

The binding of active CAP near the lac operon promoter decreases the rate of transcription of the lac operon.
__________________

Question 75

A repressor operon regulates the gene expression of anabolic pathways.
__________________

Question 76

MATCHING
Match the type of gene regulation with the process.
a.regulation of transcription
d.regulation of translation
b.regulation of mRNA processing
e.regulation of chromatin
c.regulation of mRNA transport
Unpacked heterochromatin

Question 77

MATCHING
Match the type of gene regulation with the process.
a.regulation of transcription
d.regulation of translation
b.regulation of mRNA processing
e.regulation of chromatin
c.regulation of mRNA transport
Degradation of mRNA