Deck 15: Gene Regulation in Prokaryotes

Question 1

What term describes a second level of regulation of the trp operon that occurs in TrpR^- mutants suggesting that it is repressor independent?

A)modulation
B)derepression
C)attenuation
D)amplification

Answer 1

attenuation

Question 2

The transition from transcriptional initiation to elongation involves

A)binding of sigma factor.
B)release of sigma factor.
C)release of RNA polymerase from DNA.
D)binding of RNA polymerase to DNA.
E)binding of rho factor.

Answer 2

release of sigma factor.

Question 3

How do negative regulators such as the lac repressor prevent RNA polymerase from initiating transcription?

A)by blocking passage of the polymerase through the operator
B)by forming a loop in the operator that restricts the passage of the polymerase
C)by physically blocking the DNA binding site of RNA polymerase
D)by binding to the polymerase, thus preventing its binding

Answer 3

by physically blocking the DNA binding site of RNA polymerase

Question 4

How does tryptophan, the end product of the trp operon, function in the regulation of the operon?

A)It binds to the repressor preventing it from binding to DNA thus allowing transcription of the operon.
B)It binds to the repressor and only then can the repressor bind to DNA allowing transcription of the operon.
C)It binds directly to DNA and inhibits transcription of the operon.
D)It binds to the repressor and only then can this complex bind to DNA preventing transcription of the operon.

Question 5

Proteins that undergo reversible changes in conformation when bound to another molecule are called

A)reversible peptides.
B)allosteric proteins.
C)inducer proteins.
D)repressor proteins.
E)allostatic proteins.

Question 6

Anabolic pathways involved in the synthesis of essential molecules are usually regulated by

A)end product of the pathway.
B)substrate of the pathway.
C)other metabolites that are limiting.
D)None of the choices is correct.

Question 7

In

A)inactivation of certain repressor proteins by elevated temperature.
B)denaturing of DNA in the promoters in the genes of heat sensitive proteins.
C)synthesis of alternative sigma factors at high temperatures, which then regulate transcription of heat shock genes.
D)increasing the promoter affinity of already existing polymerase sigma factors at high temperatures.
E)coli, the heat shock response, switching off the synthesis of some proteins and switching on of different proteins, is mediated by

Question 8

Transcription and translation can be coupled in bacteria but not eukaryotes since

A)there is no nuclear membrane in prokaryotes.
B)there is no nuclear membrane in eukaryotes.
C)the bacterial DNA is in the nucleoid
D)eukaryotic chromosomes are found in nucleoids.

Question 9

Which statement is true regarding global gene regulation in bacteria?

A)Sigma factors are not involved in gene regulation, just attachment of the polymerase to the promoter.
B)Alternative sigma factors recognizing different promoters carry out global gene regulation.
C)All promoters are recognized by all sigma factors.
D)coli cells devote more energy to the production of ribosomes during stress so that global gene regulation can occur.

Question 10

As a general principle of gene regulation through operons, regulatory genes encode

A)trans-acting proteins that interact with cis-acting DNA elements.
B)cis-acting proteins that interact with cis-acting DNA elements.
C)cis-acting proteins that interact with trans-acting DNA elements.
D)trans-acting proteins that interact with trans-acting DNA elements.

Question 11

Catabolic pathways that break down complex substances into more usable units are usually regulated by the

A)end products of the pathway.
B)the levels of the molecule that is to be broken down.
C)other metabolites that are limiting.
D)other enzyme binding..

Question 12

How is glucose involved in the catabolite repression of the lactose operon?

A)It has nothing to do with regulation of the lactose operon.
B)It results in decreased cAMP levels, which in turn leads to decreased CRP binding; thus the lac operon is repressed even if lactose is present along with the glucose.
C)It is also a substrate for $\beta$ -galactosidase and thus competes with lactose for this enzyme.
D)Its presence in the cell increases the amount of lac repressor in the cell.

Question 13

A common amino acid motif found in many of the polypeptides that function as repressors is

A)Leucine zipper motif.
B)Zinc finger motif.
C)Helix-turn-helix motif.
D)Helix-loop-helix motif.

Question 14

Proteins that have their activity regulated by binding of another molecule at a site other than the active site are termed

A)enzymes.
B)allosteric proteins.
C)regulatory proteins.
D)activator proteins.
E)inhibitory proteins.

Question 15

In the trp operon, attenuation occurs through translation of two Trp codons in the leader sequence.What would happen if these two codons were mutated to stop codons?

A)Region 1 will bind to region 3 in the absence of Trp..
B)The antiterminator loop will form easily.
C)Region 3 will bind to region 4 in the absence of Trp.
D)Region 3 will bind to region 1 in the presence of Trp.

Question 16

What would be the phenotype of a nonsense mutation in the lac repressor function?

A)constitutive expression of the Lac operon.
B)inducible expression of the Lac operon.
C)permanently repressed expression of the Lac operon.
D)cannot predict what would happen to expression of the Pac operon

Question 17

The critical step in the regulation of most bacterial genes occurs _____________.

A)during transcription.
B)at release of mRNA.
C)during ranslation.
D)post-translationally.

Question 18

How do positive regulators stimulate initiation of transcription by RNA polymerase?

A)by allowing passage of the polymerase through the operator
B)by binding to the polymerase and increasing its ability to initiate transcription
C)by causing the helix to unwind in the operator allowing easier initiation
D)by making the transcription start site more exposed to the polymerase

Question 19

A single DNA unit that enables the simultaneous regulation of more than one coding region in response to environmental changes is called

A)promoter.
B)operator.
C)regulator.
D)inducer.
E)operon.

Question 20

Initiation of transcription by RNA polymerase involves the binding of which of the following subunits to the core enzyme?

A)delta
B)sigma
C)gamma
D)alpha
E)zeta

Question 21

What is the relationship between the promoters for anti-sense RNA and their targets?

A)The promoters are oriented so that they transcribe opposite strands of the same piece of DNA.
B)The promoters are found in diffferent chromosomal regions but are controlled by the same sigma factors.
C)The sense and antisense RNAs use the same promoter, both RNAs are produced from a single transcript that is processed..
D)The sense and antisense RNAs are trasncribed using the same promoter that is bidirectional.

Question 22

Why is the analysis of transcriptomes useful for genetics research?

A)It reveals many aspects of gene regulation.
B)It is easy to do.
C)It can help discover non-transcribed DNA regions.
D)It directly identifies transcription factor binding sites.

Question 23

Fifteen strains of bacteria that are auxotrophic for maltose do not complement each other.The mutations in these bacteria map to the same DNA region using transformatin of random fragments of genomic DNA.There are only two unique enzymes in the maltose biosynthetic pathway and all of the mutants have a mutation in the reading frame for one or the other .What does this data suggest?

A)There are lots of enzymes in maltose metabolism.
B)All the genes for maltose metabolism are in a cluster and could be one operon.
C)There are genes scattered all over, we've simply found one set of mutants.
D)Maltose transport is very complex, these are transport mutants.

Question 24

How was E.coli was used to aid in the cloning of the bioluminescent genes from Vibrio fischeri?

A)Gene fragments from V.fischeri were transformed into E.coli and bioluminescent E coli were selected
B)Gene fragments from V.fischeri were cloned into plasmids transformed into E.coli and then reftransformed back into V.fischeri.
C)Gen fragments from E.coli were used to disrupt the bioluminescent genes of V.fischeri by homologous recombination
D)Transposons from E.coli were used to mutagenized the bioluminescent genes of V.fischeri.

Question 25

What is an advantage of using the lac regulatory regions to control the expression of exogenous proteins in bacterial cells?

A)Expression can be controlled by the addition of an inducer to the media.
B)It works in both bacterial and mammalian cells.
C)By using this regulatory region eukaryotic genomic DNA can be used for expression in bacterial cells.
D)Host regulatory mechanisms are not effective when this regulatory regions are cloned into a plasmid.

Question 26

V.fischeri senses the desity of V.fisheri cells in the environment by

A)secretion of a molecule that can then internalized and bound to a receptor in the cytoplasm.
B)cell surface receptors that interact with other cell surface receptors on other cells.
C)a cell surface receptor that binds to a molecule secreted by other cells present in the external environment.
D)a cytoplasmic receptor that binds to the lux C protein.

Question 27

The scientists who proposed the operon theory are

A)Monod and Jacob.
B)Watson and Crick.
C)Hardy and Weinberg.
D)Darwin and Mendel.
E)Hershey and Chase.

Question 28

The sigma factor that mediates a global heat shock response in E.coli is

A)sigma 70.
B)sigma 32.
C)sigma 34.
D)sigma 72.
E)sigma 36.

Question 29

Alterations to DNA sites such as promoters and operators can act

A)only in cis.
B)only in trans.
C)either in trans or in cis.
D)these terms do not apply to regulation.

Question 30

In the regulation of the trp operon, tryptophan acts as a

A)repressor.
B)attenuator.
C)activator.
D)corepressor.
E)operator.

Question 31

Small RNAs can regulate gene expression by

A)binding of target RNAs and inhibiting translation.
B)binding of rho and preventing termination.
C)binding of target promoter regions and preventing transcription.
D)binding of target operator regions and preventing transcription.

Question 32

What is one possible advantage for targeting quorum sensing mechanisms for antibiotic delveopment?

A)There is no selective advantage for cells lacking quorum sensing mechanisms
B)There is a selective advantage to those cells lacking a quorum sensing system.
C)Quorum sensing mechanisms are found in all pathogenic bacteria.
D)Quorum sensing mechanisms are only found in human pathogens.

Question 33

Why is it advantageous for transcription factors to be multimeric and for their binding sites to be clustered?

A)The affinity of the DNA-protein interactions are increased
B)The specificity of the DNA-protein interaction is increased.
C)It enhances the interaction of the DNA-proteins complexes to bind to the RNA polymerase.
D)It decreases the competition for binding between different tanrscription factors for the same regulatory region.

Question 34

Which of the following choices is NOT a correct description of a reporter gene?

A)a protein-encoding gene whose expression is easily quantifiable.
B)often fused to another protein to assess its activity.
C)often fused to another gene's regulatory region to determine control.
D)None of the choices is correct.