Deck 8: Regulation of Gene Expression

Question 1

Which of the following mutations would most likely alter the amount of a protein but not its primary structure?

A) missense mutation
B) splicing mutation
C) reverse terminator mutation
D) nonsense mutation
E) promoter mutation

Answer 1

promoter mutation

Question 2

In the lac operon, the inducer, allolactose binds to

A) the operator.
B) the promoter.
C) CRP protein.
D) the repressor.
E) RNA polymerase.

Answer 2

the repressor.

Question 3

Synthesis of tryptophan can be repressed in bacteria. The repressor protein of the tryptophan operon

A) may be activated by the binding of tryptophan.
B) may be inactivated by the binding of tryptophan.
C) may be activated by the binding of charged tryptophanyl tRNAtrp.
D) may be activated by the binding of uncharged tRNAtrp.

Answer 3

may be activated by the binding of tryptophan.

Question 4

A sequence of bases in DNA which contains structural information for one functional polypeptide is called a (an)

A) codon.
B) cistron.
C) operator.
D) polycistronic message.
E) operon.

Question 5

The region of the DNA to which RNA polymerase binds prior to the synthesis of RNA is called

A) a terminator.
B) a repressor region.
C) an operator.
D) a promoter.
E) a restriction site.

Question 6

The process of induced enzyme synthesis is best summarized by which of the following?

A) An inducing agent inactivates a repressor.
B) An inducing agent activates a derepressor.
C) The synthesis of RNA polymerase is increased.
D) Enzyme breakdown is inhibited.
E) all of the above

Question 7

A repressor attachment site is a

A) regulator gene.
B) promoter gene.
C) operator gene.
D) structural gene.
E) repressor.

Question 8

What codes for the amino acid sequence of the enzyme?

A) regulator gene
B) promoter gene
C) operator gene
D) structural gene
E) repressor

Question 9

Which one of the following is defined as a sequence of bases in DNA which contains the information for one functional polypeptide?

A) a codon
B) a cistron
C) a polysome
D) a polycistronic message
E) an operon

Question 10

In the lactose operon model, low levels of cyclic-AMP would result in

A) increased binding of the catabolite activated protein (CAP) to the promoter site.
B) decreased binding of the sigma subunit of RNA polymerase to the DNA.
C) decreased binding of the repressor to the operator site.
D) decreased inducer-repressor interaction.
E) increased transcription of the structural gene.

Question 11

Transposition is

A) the inversion of a stretch of DNA
B) the duplication of a stretch of DNA
C) the movement of a stretch of DNA from one genetic locus to the other
D) the movement of DNA Pol III along the template at l,000 nucleotides per second
E) never responsible for oncogenesis

Question 12

The binding of a repressor protein to DNA

A) occurs at the operator site.
B) stimulates translation.
C) stimulates RNA polymerase.
D) causes mutation.
E) requires an inducer.

Question 13

The dnaA protein

A) is a single stranded DNA binding protein.
B) binds to the origin of replication to prevent transcriptional initiation.
C) binds to an alternative site for DNA replication.
D) binds to the genomic DNA origin of replication to initiate DNA replication.
E) binds to the dnaB-dnaC protein complex after initiation.

Question 14

Which of the following statements are true about dolichol? 1. It is a vesicle in which N?
Linked glycosylation of proteins takes place. 2. It is a polyisoprenoid. 3. It serves as the active donor of an oligosaccharide unit to proteins. 4. It is an enzyme which catalyzes the glycosylation of proteins. 5. It is involved in O?
Glycosylation of proteins.

A) only 1 and 3 are true
B) only 2 and 5 are true
C) only 1 and 4 are true
D) only 2 and 3 are true
E) none is true

Question 15

Which of the following happens when cAMP binds to the catabolite activator protein (CAP)?

A) CAP dissociates from its specific site upstream of the lac operon.
B) Synthesis of beta?galactosidase stops.
C) Binding of RNA polymerase to the promoter is enhanced.
D) The lac repressor dissociates from the operator.
E) None is correct.

Question 16

A codon consists of

A) one molecule of amino acyl-tRNA.
B) an individual ribosome.
C) three consecutive nucleotide units of an mRNA.
D) two complementary base pairs.
E) three consecutive cistrons.

Question 17

In bacterial mismatch repair the repair enzyme complex recognizes the parental strand since

A) the parental strand has histones attached.
B) the daughter strand is always in fragments.
C) the parental strand contains more thymines.
D) the parental DNA is methylated.
E) the repair complex cannot tell the difference.

Question 18

Gene expression can be regulated at the level of polyadenylation.

A) prokaryotes
B) eukaryotes
C) Both
D) Neither

Question 19

Which of the following happen when cAMP binds to the catabolite activator protein (CAP)?

A) CAP comes off of its specific site upstream of the lac operon.
B) Synthesis of beta?galactosidase stops.
C) Binding of RNA polymerase to the promoter is enhanced.
D) The lac repressor comes off of the operator.
E) none is correct

Question 20

Which of the following is characteristic of prokaryotic mRNAs?

A) They have a 5' cap.
B) They are polyadenylated.
C) They are polycistronic.
D) They must be transported to the cytoplasm.
E) Introns are removed from them.

Question 21

Uses attenuation as a mechanism to control expression of its genes.

A) lac operon
B) trp operon
C) Both
D) Neither

Question 22

Adenylate cyclase is the enzyme which converts ATP to 5'-cAMP. What is the expected effect on the in vivo expression of the lactose operon of a nonsense mutation in the adenylate cyclase structural gene (which totally inactivates the enzyme)?

A) No effect under any environmental conditions.
B) the operon is transcribed at a high rate when cells are grown in a mixture of glucose plus lactose.
C) The operon is transcribed at a high rate when cells are grown in a mixture of glucose plus lactose.
D) The operon is transcribed at a high rate in the presence of lactose but a low rate in the presence of glucose and lactose.
E) The operon is not efficiently transcribed in the presence of lactose.

Question 23

Which of the following statements about regulation of the trp operon are true? When the Trp concentration in the cell is very low, 1. ribosomes stall at Trp codons in the attenuator. 2. RNA polymerase terminates transcription of the trp operon prematurely. 3. the secondary structure of the RNA transcribed from the leader region changes. 4. enzymes which catalyze the synthesis of Trp are made in greater abundance.

A) only 1, 2 and 3 are true
B) only 2, 3 and 4 are true
C) only 1, 3 and 4 are true
D) only 1 and 3 are true
E) all are true

Question 24

Phenotypic repression can be mediated by:

A) a repressor protein that is activated by the removal of a small molecule inducer (anti?repressor)
B) a repressor protein that requires a small molecule corepressor for activity
C) an activator protein that is inactivated by removal of an essential coactivator
D) an activator protein that is inactivated by a small molecule anti?activator
E) All of the above

Question 25

The SREBP-1a domain of SREBP (sterol responsive element-binding protein 1a) must be transported into the nucleus for LDL receptor synthesis to occur. From which membrane is this protein released for transfer to the nucleus?

A) Cis-Golgi
B) ER
C) Mitochondrion
D) Nuclear
E) Plasma

Question 26

What family of genes are frequently carried by bacterial transposons?

A) Antibiotic resistance
B) F factor
C) Origins of replication
D) Restriction endonucleases
E) Toxin production

Question 27

Where do insulator sequences occur in a gene?

A) Between start and enhancer
B) Between TATA box and enhancer
C) Downstream from enhancer
D) Upstream from the TATA box
E) Within the enhancer sequence

Question 28

The following protein motifs participate directly in DNA binding

A) helix-loop-helix, zinc finger, leucine zipper
B) zinc finger, leucine zipper, homeodomain
C) helix-turn-helix, zinc fingers, homeodomain
D) helix-turn-helix, helix-loop-helix, zinc finger
E) helix-loop-helix, leucine zipper, homeodomain

Question 29

In the lac system, catabolite repressor protein reacts with

A) lac operator and cAMP.
B) lac promoter and glucose.
C) lac operator and lactose.
D) lac promoter and cAMP.
E) lac repressor and lactose.

Question 30

A protein motif found in several eukaryotic transcription factors with a function in protein dimerization is the

A) leucine zipper.
B) helix-turn-helix.
C) zinc finger.
D) heme pocket.

Question 31

Mutation of the repressor protein to an inactive form leads to constitutive (always on) expression of the operon.

A) lac operon
B) trp operon
C) Both
D) Neither

Question 32

All of the following statements concerning the lactose operon are correct EXCEPT

A) transcription is regulated by both positive and negative acting proteins.
B) the mRNA transcribed from the operon corresponding to the Z, Y, and A genes is very unstable.
C) cyclic AMP modulates transcription of the lac operon in response to external glucose levels.
D) the repressor binds specifically to the CAP protein.
E) the level of induction of the lactose operon is dependent on the concentration of inducer.

Question 33

A mutation in the lac operator that blocks the binding of the lac repressor [all of the following EXCEPT]:

A) causes constitutive expression of the z gene.
B) leads to an inactivation of the lac repressor protein.
C) eliminates the transcriptional induction of the z gene by allolactose.
D) causes constitutive expression of the permease gene (y gene).
E) is active only in a cis arrangement.

Question 34

Allolactose and cAMP function in the regulation of the lactose operon in

A) decreasing the affinity of their respective proteins for DNA.
B) acting as allosteric effectors of their respective proteins.
C) increasing the affinity of their respective proteins for DNA.
D) covalently modifying their respective proteins.
E) coli by binding to two different regulatory proteins. In doing so they are

Question 35

In the Holliday model for recombination, which is not true?

A) One of two recombination products are formed depending on how the branch is cleaved.
B) Strand exchange leads to an intermediate structure with crossed single strands.
C) Two homologous duplexes are aligned.
D) The branch can move along the strands leading to additional strand exchange.
E) The strand exchange is initiated by DNase I nicking.

Question 36

Which of the following substances binds to lac repressor?

A) lac promoter DNA
B) lactose
C) allolactose
D) beta-galactosidase

Question 37

Positive regulation of gene expression has a specific meaning relating to the effect of a regulatory protein on the gene in question. In which of the following systems does positive regulation occur?

A) the lac repressor lac operator system
B) catabolite repression
C) the trp operon
D) the lysogenic pathway of lambda.
E) none is true

Question 38

Which of the following provides information for the structure of specific proteins?

A) Operon
B) Structural genes
C) Regulator genes
D) Operator genes
E) Mutator genes

Question 39

Polycistronic transcripts

A) are usually observed in eukaryotes.
B) encode multiple functionally unrelated proteins.
C) permit the coordinated production of a set of proteins by control of transcription from a single promoter region.
D) are spliced in spliceosomes to produce several functional mRNAs.

Question 40

What is the most expected effect of a deletion mutation covering the promoter sequence of the lactose operon?

A) Loss of catabolite repression of beta-galactosidase.
B) Loss of transcription of the beta-galactosidase gene in the presence of lactose.
C) Transcription of the beta-galactosidase gene in the absence of lactose.
D) Transcription of the beta-galactosidase gene only in the presence of high levels of lactose.
E) Constitutive synthesis of beta-galactosidase in an F' merodiploid.

Question 41

Transcriptional cis acting elements often show dyad symmetry.

A) prokaryotes
B) eukaryotes
C) Both
D) Neither

Question 42

What are the function of homeodomain factors

A) Alternative splicing of immunoglobin genes
B) Induction of xenobiotic metabolism
C) Organization of body parts
D) Steroid hormone receptors
E) Suppression of carcinogenesis

Question 43

Promoter elements that regulate expression of genes transcribed by RNA polymerase III are commonly found:

A) upstream of the structural gene.
B) overlapping the TATA element.
C) within the structural gene.
D) downstream of the structural gene.
E) in either orientation.

Question 44

Which of the following binds the repressor protein during induction?

A) operator gene
B) regulator gene
C) structural gene
D) promoter
E) none of the above

Question 45

Which of the following protein motifs can be involved in dimerization of transcription factors?

A) Helix-turn-helix
B) Asn-X-Ser/Thr
C) leucine zipper
D) zinc fingers

Question 46

In the presence of isopropylthiogalactoside (IPTG) and glucose, transcription of the lac operon

A) will be at maximal levels because IPTG is a nonmetabolizable inducer.
B) will be slightly above basal levels due to IPTG causing the release of repressor from the operator site but the presence of glucose prevents maximal induction.
C) will be at basal levels because the induction of the lac operon requires the presence of lactose.
D) will terminate as IPTG is an inhibitor of
E) coli RNA polymerase.

Question 47

An inducer attachment site is a

A) regulator gene.
B) promoter gene.
C) operator gene.
D) structural gene.
E) repressor.

Question 48

Organization of multiple genes into operons in prokaryotes provides for:

A) alternate gene expression
B) global regulation
C) DNA amplification
D) coordinate expression of genes involved in a related process

Question 49

Which of the following is not a mechanism for regulation of eukaryotic gene expression?

A) phosphorylation of transcription factors
B) alternative splicing
C) deletion of genes
D) RNA editing
E) alternative polyadenylation

Question 50

Regulation of the trp operon at the level of transcription initiation is an example of

A) a positive inducible system.
B) a positive repressible system.
C) a negative inducible system.
D) a negative repressible system.
E) a constitutive system.

Question 51

The TATA box is bound by

A) RNA polymerase II.
B) RNA polymerase III.
C) DNA polymerase alpha.
D) lac repressor.
E) TFIID.

Question 52

A codon is

A) the signal for the starting point of transcription.
B) a specific nucleotide sequence of an mRNA molecule read in the 5' to direction.
C) part of an open, unbonded loop of a tRNA molecule.
D) a nucleotide triplet of rRNA, read in the 5' to direction.
E) none of the other answers is correct.

Question 53

A transcriptional repressor plays a strong role in the regulation of this operon.

A) lac operon
B) trp operon
C) Both
D) Neither

Question 54

The lac repressor can function as an inhibitor of transcription of the lactose operon because of its ability to

A) covalently modify promoter DNA.
B) bind the allosteric effector cAMP.
C) stabilize nucleosomes.
D) bind operator DNA with high affinity.

Question 55

Catabolite activator protein (CAP) increases transcription from the lactose operon by

A) binding lactose which releases the repressor from the operator.
B) directly increasing free cellular cAMP concentrations.
C) binding the operator and competing for repressor binding.
D) stabilizing the binding of RNA polymerase to the promoter.
E) preventing the degradation of RNA polymerase.

Question 56

Maximal induction of the lactose operon in

A) glucose is plentiful and lactose is limiting.
B) lactose is plentiful and glucose is limiting.
C) both glucose and lactose are plentiful.
D) both glucose and lactose are limiting.
E) coli occurs when

Question 57

Regulation of the lac operon in

A) Beta-galactosidase levels can be up and down regulated solely by transcriptional controls.
B) Beta-galactosidase levels are regulated by both transcriptional and translation controls.
C) Increased mRNA stability can maintain Beta-galactosidase levels.
D) cAMP can help to repress Beta-galactosidase levels.
E) coli illustrate which of the following?

Question 58

The repressor protein requires the end product created by the enzymes of this operon for repression.

A) lac operon
B) trp operon
C) Both
D) Neither

Question 59

Which eukaryotic transcription factor is thought to mediate transient opening of the DNA duplex and phosphorylation of RNA polymerase II, thus initiating transcription?

A) TFIIA
B) TFIIB
C) TFIIE
D) TFIIF
E) TFIIH

Question 60

Prokaryotic gene regulation employs

A) enhancers.
B) spliceosomes.
C) signal sequences.
D) operons.
E) locus control regions.

Question 61

Repressors can function in the regulation of gene expression by

A) altering the conformation of RNA polymerase.
B) blocking RNA polymerase access to the promoter.
C) binding to newly synthesized RNA.
D) dissociating RNA polymerase into its subunits.
E) preventing translation of mRNA.

Question 62

Repressors function in the regulation of gene expression by

A) altering the conformation of RNA polymerase.
B) binding to the operator region of DNA.
C) hybridizing to the promoter region of DNA.
D) mediating removal of the sigma subunit of RNA polymerase.
E) preventing translation of RNA.

Question 63

High level expression of the lac operon requires

A) high lactose, high glucose.
B) high glucose, low lactose.
C) low glucose, low lactose.
D) low glucose, high lactose.
E) any of these will give high level expression.

Question 64

Promoter elements that regulate expression of genes transcribed by RNA polymerase III are commonly found

A) upstream of the structural gene.
B) overlapping the TATA element.
C) within the structural gene.
D) downstream of the structural gene.
E) in either orientation.

Question 65

High level expression of the lac operon requires

A) high lactose, high glucose.
B) high glucose, low lactose.
C) low glucose, low lactose.
D) low glucose, high lactose.
E) any of these will give high level expression.

Question 66

The function of the zinc fingers in a nuclear hormone receptor is to

A) accelerate the translocation of the receptor protein to the nucleus.
B) bind to specific DNA sequences.
C) interact with a steroid-like ligand.
D) modulate ribosome translational activity.
E) transport divalent cations to the nucleolus.

Question 67

A mutation in the lac operator that blocks the binding of the lac repressor [all of the following EXCEPT]:

A) causes constitutive expression of the z gene
B) leads to an inactivation of the lac repressor protein
C) eliminates the transcriptional induction of the z gene by allolactose
D) causes constitutive expression of the permease gene (y gene)
E) is active only in a cis arrangement

Question 68

Regulatory systems in which the promoter-recognition properties of RNA polymerase are altered are likely to be:

A) specific for a single gene
B) specific for a single operon
C) global
D) translational
E) mediated by DNA inversion

Question 69

A repressor binding site on bacterial DNA is called a

A) co-repressor.
B) promoter.
C) operator.
D) attenuator.
E) enhancer.

Question 70

The phenomena of induction and repression can occur because

A) the genes for enzyme synthesis can be produced as required.
B) enzyme synthesis involves both structural genes and regulatory genes.
C) feedback inhibitors control the activity of enzymes without affecting enzyme synthesis.
D) derepression involves the conversion of inactive zymogen to active enzyme.
E) enzyme induction is due to allosteric modification of RNA polymerase.

Question 71

Which of the following is a biological amplification event in the lac operon system?

A) Binding of the inducer to the repressor.
B) Transcription of the beta-galactosidase gene by RNA polymerase.
C) Interaction of the CAP protein with cAMP.
D) Association of the RNA polymerase with the lac promoter region.
E) All of the above.

Question 72

In the lac operon, the inducer, allolactose binds to

A) the operator.
B) the promoter.
C) CRP protein.
D) the repressor.
E) RNA polymerase.

Question 73

An inducible enzyme is one that

A) is produced only when it is needed.
B) is always present.
C) is always under allosteric regulation.
D) none of the above.

Question 74

Which of the following is true concerning gene expression?

A) An increase in expression implies an increase in transcriptional initiation.
B) mRNA levels are determined solely by the rate of transcriptional initiation.
C) Attenuation is a well-described and common mechanism for controlling gene expression in eukaryotic cells.
D) Regulation of expression occurs at many levels from transcriptional initiation to protein degradation.
E) Gene copy number does not influence the level of gene expression.

Question 75

Specific DNA-protein interactions

A) require that the DNA strands separate so that the protein can form hydrogen bonds with the bases.
B) involve regions by dyad symmetry in the DNA.
C) are regulated by phosphorylation of certain DNA sites.
D) involve covalent interactions between the DNA and protein.

Question 76

Which of the following occur as a result of the inducer (lactose or a derivative of lactose) binding to the lac repressor protein? 1. RNA polymerase transcribes the /lac operon. 2. Catabolite activator protein binds to a specific site on the DNA. 3. There is a conformational change in the repressor. 4. The amount of beta?
Galactosidase increases in the cell.

A) only 1, 2 and 3 are true
B) only 2, 3 and 4 are true
C) only 1, 3 and 4 are true
D) only 1 and 3 are true
E) all are true

Question 77

The TATA box is bound by

A) RNA polymerase II.
B) RNA polymerase III.
C) DNA polymerase alpha.
D) lac repressor.
E) TFIID.

Question 78

Basic region? leucine zipper (bZIP) transcription factors function in the initiation of transcription by

A) phosphorylating RNA polymerase.
B) binding to specific DNA sequence elements.
C) acetylating histones at the promoter.
D) binding to the TATA box.

Question 79

Prokaryotic gene regulation employs

A) enhancers.
B) spliceosomes.
C) signal sequences.
D) operons.
E) locus control regions.

Question 80

Repressors function in the regulation of gene expression by:

A) altering the conformation of RNA polymerase.
B) binding to the operator region of DNA.
C) hybridizing to the promoter region of DNA.
D) mediating removal of the sigma subunit of RNA polymerase.
E) preventing translation of RNA.