BIOL 2051 - ch 7, 9, 12, 25, 26

Regulation of enzyme activity occurs

A) at the start of transcription.
B) at the start of translation.
C) posttranslationally.

D) at any point on the enzymatic production pathway.

C) posttranslationally.

When arginine is added to a culture already growing exponentially in a medium without arginine, what occurs?
A) All cellular growth ceases.
B) Growth continues, but the production of enzymes required for the synthesis of arginine ceases.

C) Growth continues, but the production of enzymes required for the synthesis of arginine increases.
D) The cell returns to the lag stage of growth to synthesize the proteins necessary for the metabolism of arginine.

B) Growth continues, but the production of enzymes required for the synthesis of arginine ceases.

Regulatory proteins
A) are influenced by small molecules.
B) bind to specific DNA sites.
C) regulate transcription.
D) regulate transcription, bind specific DNA sites, and can be influenced by small molecules

D) regulate transcription, bind specific DNA sites, and can be influenced by small molecules

A protein region with a specific function and structure is called a A) conserved site.
B) domain.
C) locale.

D) motif.

B) domain.

Transcriptional regulators bind most frequently at the ________ site of DNA.

A) major groove
B) minor groove
C) histone complex

D) primary supercoil

A) major groove

Which type of regulator(s) specifically binds to operator regions of DNA?

A) Activators
B) Activators and inducers
C) Repressors

D) Repressors and corepressors

C) Repressors

The lac operon is an example of ________ control in which the presence of an ________ is required for transcription to occur.
A) negative / activator
B) negative / inducer

C) positive / activator
D) positive / inducer

B) negative / inducer

Enzyme induction occurs
A) when the substrate is present.
B) when the organism is environmentally stressed.
C) continuously.
D) when the substrate is depleted.

A) when the substrate is present.

Considering the catabolite repression mechanism, which observation would make you suspect it IS occurring?
A) CRP bound to promoter sites
B) Elevated levels of transcripts for maltose and sucrose catabolism

C) Relatively low intracellular cyclic AMP levels
D) RNA polymerase bound to biosynthetic promoter sequences

C) Relatively low intracellular cyclic AMP levels

During a growth curve of Aliivibrio fischeri, when would you expect to see the strongest bioluminescence?
A) Lag phase
B) Early to middle log phase

C) Late log to early stationary phase
D) Middle to late stationary phase

C) Late log to early stationary phase

What occurs when an inducer is added to an environment containing an organism with a metabolic pathway controlled by a repressor?
A) The inducer combines with the repressor and activates the pathway.
B) The inducer combines with the repressor and inactivates the pathway.

C) The inducer combines with the substrate and blocks induction.
D) The inducer does not combine with, but functions as a chaperone molecule for, the enzyme- substrate complex.

B) The inducer combines with the repressor and inactivates the pathway.

Which of the following do NOT bind to the promoter sequence during regulation?

A) Activators
B) Inducers
C) Repressors

D) None of these bind directly to the promoter sequence.

D) None of these bind directly to the promoter sequence.

Cyclic AMP is synthesized from ATP by an enzyme called ________ which is involved in ________.
A) adenylate cyclase / catabolite repression
B) adenylate cyclase / transcriptional activation

C) cAMP receptor protein (CRP) synthase / catabolite repression
D) cAMP receptor protein (CRP) synthase / transcriptional activation

A) adenylate cyclase / catabolite repression

In negative control of transcription by the lac operon, how does the presence of an inducer affect transcription?
A) The inducer binds to the operator.
B) The inducer does not bind to the operator.

C) The inducer causes the repressor to bind to the operator.
D) The inducer prevents the repressor from binding to the operator.

D) The inducer prevents the repressor from binding to the operator.

Mechanisms for controlling enzyme activity include all of the following EXCEPT

A) degradation of the enzyme.
B) feedback inhibition.
C) covalent modification of the enzyme.

D) addition of short sections of new amino acid sequence.

D) addition of short sections of new amino acid sequence.

The function of a kinase is

A) methylation.
B) response regulation.
C) phosphorylation.

D) glycosylation.

C) phosphorylation.

The promoters of positively controlled operons require activator proteins because
A) RNA polymerase easily recognizes the consensus sequence.
B) they are required to inactivate the repressor proteins.
C) the promoters bind RNA polymerase weakly and utilize activator proteins to help RNA polymerase recognize the promoter.

D) they are needed to bind to the allosteric site of RNA polymerase.

C) the promoters bind RNA polymerase weakly and utilize activator proteins to help RNA polymerase recognize the promoter.

Transcriptional control in Archaea most closely resembles that in ________ and utilizes ________.
A) bacteria / regulatory proteins
B) eukaryotes / regulatory proteins

C) bacteria / transcription factors
D) eukaryotes / transcription factors

A) bacteria / regulatory proteins

The most frequent way in which small regulatory RNA molecules exert their effects is by

A) base pairing with other RNA molecules that have regions of complementary sequence.
B) binding to a repressor and repressing enzyme transcription.
C) acting as an inducer that then binds to an activator protein to allow transcription to proceed.

D) signal transduction.

A) base pairing with other RNA molecules that have regions of complementary sequence.

________ pathways typically rely on ________ proteins to inhibit mRNA synthesis.

A) Anabolic / repressor
B) Catabolic / repressor
C) Anabolic / activator

D) Catabolic /activator

A) Anabolic / repressor

________ pathways typically utilize ________ proteins that stimulate binding of RNA polymerase to DNA.
A) Anabolic / repressor
B) Catabolic / repressor

C) Anabolic / activator
D) Catabolic / activator

D) Catabolic / activator

In Bacteria, sensor kinases that respond to extracellular signals transfer this signal to the cytoplasmic machinery by typically phosphorylating which residues?
A) Histidine
B) Serine

C) Threonine
D) Tyrosine

A) Histidine

Quorum sensing is a regulatory system that requires a certain cell density to work effectively. Each of the following activities utilizes quorum sensing EXCEPT
A) Staphylococcus aureus infection.
B) transition of Candida albicans from budding yeast to elongated filaments.

C) flagella synthesis in Proteus vulgaris.
D) light emission by Aliivibrio fischeri.

C) flagella synthesis in Proteus vulgaris.

Chemotaxis in bacteria occurs through the use of

A) adaptation.
B) quorum sensing.
C) autoinduction.

D) a modified two-component system.

D) a modified two-component system.

Which statement is TRUE of two separate regulators controlling one individual operon?

A) The two regulators themselves must respond to different signals, which enables both to control the operon differently.
B) One regulator will likely control the transcription of one section of the operon, whereas the other regulator will control the other component.

C) One regulator will bind to the operator region whereas the other will bind to the promoter region so they can co-occur and co-regulate the operon.
D) Two regulators trying to control the same operon will likely result in only one being maintained after several generations.

A) The two regulators themselves must respond to different signals, which enables both to control the operon differently.

How would you design an sRNA to bind to a sequence?
A) Select six continuous nucleotides from the sequence
B) Take the complementary sequence of six continuous nucleotides

C) Select 200 continuous nucleotides from the sequence
D) Take the complementary sequence of 200 continuous nucleotides

D) Take the complementary sequence of 200 continuous nucleotides

When the nontemplate strand of a gene is transcribed into RNA, what is likely to result?
A) A complementary sRNA will bind to it and form a functional ribozyme with secondary structure.
B) It will complementarily bind to the gene sequence, form a hairpin loop, and transcriptionally repress the gene.

C) The complementary mRNA transcribed from the template strand will bind to it and halt its translation.
D) A global regulator will identify this as a stress, respond by inducing ribonuclease production, and it will be degraded.

C) The complementary mRNA transcribed from the template strand will bind to it and halt its translation.

Based on our understanding of the early stages of life, ________ is/are thought to be one of the earliest forms of metabolic regulation that evolved.
A) attenuation
B) feedback inhibition

C) riboswitches
D) transcription factors

C) riboswitches

Attenuation is a type of regulation that can control

A) allosteric enzyme activity.
B) transcriptional activity exclusively.
C) translational activity exclusively.

D) both transcriptional and translational activity.

B) transcriptional activity exclusively.

Which of the following is a characteristic of an isoenzyme?
A) More than one enzyme is regulated by the same mechanism.
B) The same reaction can be catalyzed by multiple enzyme variants.
C) Multiple binding sites on the same enzyme enable multiple regulation mechanisms.

D) More than one gene makes the same enzyme.

B) The same reaction can be catalyzed by multiple enzyme variants.

Which regulatory mechanism does NOT depend on a conformational change in protein/enzyme structure to change activity?
A) Attenuation
B) Catabolite repression

C) Feedback inhibition
D) Negative control

A) Attenuation

An organism grown in nutrient rich broth to high turbidity always produces a blue pigment. When a large inoculum is transferred to a nutrient rich agar plate, it also appears blue. A researcher noticed that this never happens when very small colonies are grown on low nutrient agar plates, however. What is the most plausible conclusion?

A) Large populations enabled the differentiation of a subpopulation of cells that created the blue pigment.
B) Only high nutrient conditions provide enough energy for cells to produce this secondary metabolite that appears blue.

C) Production of the blue pigment production is linked to quorum sensing.
D) The strong gradient from very high to low nutrient bioavailability induces production of the blue metabolite.

C) Production of the blue pigment production is linked to quorum sensing.

A bacterium that either partially or fully catabolizes an acyl-homoserine lactone will likely disrupt
A) attenuation.
B) chemotaxis.

C) endospore formation.
D) quorum sensing.

D) quorum sensing.

Phosphorylation of ________ regulates which direction a flagellum rotates, thus controlling whether an organism runs or tumbles.
A) CheAW
B) CheB

C) CheY
D) CheZ

C) CheY

Which organism would likely harbor the most two-component regulatory systems?

A) An archaeon living in an extreme environment
B) A bacterium occupying a heterogeneous niche with high nutrient mixing
C) An organism capable of quorum sensing

D) A parasitic bacterium living inside another organism

B) A bacterium occupying a heterogeneous niche with high nutrient mixing

How is the activity of a riboswitch controlled?

A) By other riboswitches
B) Metabolite binding can change its structure.
C) Sigma factor binding alters its structure.

D) Small RNA complementary binding disrupts its function.

B) Metabolite binding can change its structure.

A mutation in the gene encoding the lactose repressor (LacI) that prevents lactose from binding to the LacI protein would result in
A) constant expression of the lac operon in the absence of lactose.
B) constant repression of the lac operon in the absence of lactose.

C) constant expression of the lac operon in the presence of lactose.

D) constant repression of the lac operon in the presence of lactose.

D) constant repression of the lac operon in the presence of lactose.

Why are two-component regulatory systems particularly useful for controlling gene expression in response to environmental signals?
A) Two proteins controlling a gene means there are two chances to activate a gene.
B) Two proteins delay the response time so the cell can be sure the change is permanent.

C) One of the two proteins can be exposed to the external environment to receive a signal.

D) Phosphorylation is a permanent change so genes are always turned on after signal.

D) Phosphorylation is a permanent change so genes are always turned on after signal.

In order for the helix-turn-helix motif to bind to DNA, the ________ must fit into the major groove of the DNA.
A) homeotic switches
B) recognition helix

C) operator
D) zinc fingers

B) recognition helix

Infection by the foodborne pathogen E coli O157:H7 involves all of the following host and pathogen signaling molecules EXCEPT
A) AI-3.
B) MCP.

C) epinephrine.
D) norepinephrine.

B) MCP.

Global regulatory systems include all of the following EXCEPT

A) amino acid synthesis.
B) transformation.
C) heat shock response.

D) anaerobic respiration.

A) amino acid synthesis.

When more than one operon is under the control of a single regulatory protein, the operons are collectively called a(n)
A) regulon.
B) operator.

C) autoinduce.
D) riboswitch.

A) regulon.

Most riboswitches control

A) transcription.
B) translation.
C) ribosome synthesis.

D) tRNA synthesis.

B) translation.

PII proteins are a family of signal-transducing proteins that regulate ________ during nitrogen metabolism.
A) transcription factors
B) enzymes

C) membrane transport proteins
D) PII proteins regulate each of the above during nitrogen metabolism.

D) PII proteins regulate each of the above during nitrogen metabolism.

All of the following are functions of heat shock proteins in bacteria EXCEPT

A) prevention of inappropriate protein subunit aggregation.
B) degradation of denatured proteins.
C) responding to exposure to high levels of ethanol.

D) stimulation of binary fission.

D) stimulation of binary fission.

(T/F) Proteins required at approximately the same level throughout a cell's growth cycle are often not subject to regulatory mechanisms and are constitutively synthesized.

true

(T/F) Short regions at the beginning and end of gene sequences are not translated into proteins.

true

(T/F) Small molecules usually act directly (rather than indirectly) in regulating transcription.

false

(T/F) A common structure for proteins that bind DNA is helix-turn-helix.

true

(T/F) The residues in a DNA-binding protein that interact with DNA usually correspond to each other according to the amino acids encoded by the DNA. For example, a DNA sequence containing AGC-AGA-CAG which encodes for Ser-Arg-Gln would likely have a DNA-binding protein with the sequence Ser-Arg-Gln.

false

(T/F) Some proteins that bind to DNA block transcription, whereas other proteins activate transcription.

true

(T/F) Enzyme repression typically affects catabolic pathways.

false

(T/F) Depending on the type of regulatory mechanism, activators and repressors can bind to operator regions which control transcription.

false

(T/F) A regulon is composed of at least two operons regulated by the same protein.

true

(T/F) The preferential use of glucose over other available carbon substrates for growth is mechanistically explained by catabolite repression.

true

(T/F) Proteins and RNA molecules that are needed in the cell at about the same level under all growth conditions, require constitutive expression.

true

(T/F) A two-component regulatory system usually involves both the sensor and response proteins being subject to phosphorylation.

true

(T/F) Cyclic AMP (cAMP) is involved in the global regulation of catabolic pathways in Escherichia coli, including the lac operon. A high activity of the enzyme adenylate cyclase, which makes cAMP, is suggestive of catabolite repression.

false

(T/F) Once cytoplasmic sensor proteins involved in chemotaxis regulation are phosphorylated, a cascade of other phosphate-transferring mechanisms provides ATP to rotate flagella.

false

(T/F) In most cases, the first product of a particular biosynthetic pathway represses the enzymes of the pathway.

false

(T/F) In catabolic repression, cells always use the least abundant carbon source first.

false

(T/F) The small size of prokaryotic cells limits their ability to respond to spatial gradients of a chemical.

true

(T/F) Adaptation is based on the level of phosphorylation of MCPs.

false

(T/F) Quorum sensing relies upon a large cell population which then turns on transcription.

true

(T/F) During chemotaxis, attractants increase the rate of autophosphorylation, whereas repellants decrease this rate.

false

(T/F) Heat shock proteins are produced in high number to minimize damaging effects during high heat conditions, in addition to other stress signals unrelated to heat such as ultraviolet radiation.

true

(T/F) Regulation of transcription in Archaea is more similar to that which occurs in eukaryotes than in bacteria.

false

(T/F) The stringent response is a mechanism used by bacteria that provides increased ability to survive in environments lacking nutrients.

true

(T/F) When environmental levels of amino acids become limited, synthesis of mRNA, rRNA, and tRNA increases immediately.

false

(T/F) In many environments, the limiting nutrient for bacterial growth is phosphorus.

true

(T/F) Multiple mechanisms for small RNA (sRNA)-mediated translational regulation exist, but all are unified by inactivating protein synthesis of the target mRNA.

false

A mutant that has a nutritional requirement for growth is an example of a(n)

A) autotroph.
B) auxotroph.
C) heterotroph.

D) organotroph.

B) auxotroph.

Consider a mutation in which the change is from UAC to UAU. Both codons specify the amino acid tyrosine. Which type of point mutation is this?
A) Silent mutation
B) Nonsense mutation

C) Missense mutation
D) Frameshift mutation

A) Silent mutation

A mutation that readily reverses to restore the original parental type would most likely be due to a(n)
A) deletion.
B) insertion.

C) point mutation.
D) frameshift mutation.

C) point mutation.

Which process listed below allows genetic material to be transferred from a virus-like particle that lacks genes for its own replication?
A) Conjugation of an F+ plasmid
B) Gene transfer through a gene transfer agent

C) Transduction by a dsDNA phage Mu
D) Transformation of a linear piece of DNA

B) Gene transfer through a gene transfer agent

The mutagens 2-aminopurine and 5-bromouracil are examples of

A) alkylating agents.
B) nucleotide base analogs.
C) chemicals reacting with DNA.

D) None of the answers are correct.

B) nucleotide base analogs.

The killing of cells by UV irradiation involves

A) absorption at 260 nm by proteins only.
B) absorption at 260 nm by RNA only.
C) formation of pyrimidine dimers.

D) formation of purine dimers.

C) formation of pyrimidine dimers.

Ionizing radiation does NOT include

A) gamma rays.
B) UV rays.
C) X-rays.

D) cosmic rays.

B) UV rays.

Which of the following methods may introduce foreign DNA into a recipient?

A) Transformation
B) Transduction
C) Conjugation

D) Transformation, transduction, and conjugation

D) Transformation, transduction, and conjugation

The uptake of free DNA from the environment is referred to as ________, while the transfer of DNA with cell-to-cell contact is known as ________.
A) transformation / conjugation
B) transduction / conjugation

C) conjugation / transformation
D) transformation / transduction

A) transformation / conjugation

Which of the following is NOT required for homologous recombination?

A) An Hfr chromosome
B) RecA
C) Proteins having helicase activity

D) Endonuclease

A) An Hfr chromosome

Consider the following experiment. First, large populations of two mutant strains of Escherichia coli are mixed, each requiring a different, single amino acid. After plating them onto a minimal medium, 45 colonies grew. Which of the following may explain this result?
A) The colonies may be due to back mutation (reversion).
B) The colonies may be due to recombination.
C) Either A or B is possible.
D) Neither A nor B is possible.

C) Either A or B is possible.

You have performed the following mating experiment using Hfr and F-strains of Escherichia

coli: Hfr (thr + leu+ gal+ strs) × F- (thr- leu- gal- strr). Which of the following selective media would you use to score recombinant colonies?
A) Minimal medium
B) Minimal medium + streptomycin

C) Minimal medium + threonine
D) Minimal medium + streptomycin + threonine

B) Minimal medium + streptomycin

Horizontal gene transfer in Archaea
A) is infrequent in nature and therefore difficult to use for genetic studies in the laboratory.
B) has not been documented, thus all genetic studies of archaea are done via genomic sequencing.
C) frequently occurs in nature and has been used to perform genetic studies in the laboratory as well.
D) frequently occurs in nature, but there are very few laboratory studies because archaea do not cause human disease.

C) frequently occurs in nature and has been used to perform genetic studies in the laboratory as well.

The minimal amount of genetic information required for specialized transduction would include
A) the att region.
B) the cos site.

C) a helper phage.
D) the att region, cos site, and a helper phage.

D) the att region, cos site, and a helper phage.

Lysogeny probably carries a strong selective advantage for the host cell because it

A) prevents cell lysis.
B) confers resistance to infection by viruses of the same type.
C) confers resistance to infection by viruses of a different type (or strain).

D) confers resistance to infection by many virus types and prevent cell lysis.

B) confers resistance to infection by viruses of the same type.

A plasmid may
A) replicate independently of the chromosome.
B) be transferred cell-to-cell during conjugation.
C) be integrated into the chromosome.
D) replicate independently of the chromosome, integrate into the chromosome, or be transferred cell-to-cell during conjugation.

D) replicate independently of the chromosome, integrate into the chromosome, or be transferred cell-to-cell during conjugation.

Plasmids that govern their own transfer are known as

A) transformable.
B) transmutable.
C) conjugative.

D) transfective.

C) conjugative.

Homologous recombination has been observed in

A) Archaea.
B) Bacteria.
C) Eukarya.

D) All three domains (Archaea, Bacteria, and Eukarya).

D) All three domains (Archaea, Bacteria, and Eukarya).

Hfr strains of Escherichia coli

A) do not possess an F factor.
B) have the F factor as a plasmid.

C) have an integrated F factor.

D) transfer the complete F factor to recipient cells at a high frequency.

C) have an integrated F factor.

F+ strains of Escherichia coli
A) do not have an F factor.
B) have the F factor as a plasmid.
C) have an integrated F factor.
D) transfer the F factor to recipient cells at a high frequency.

B) have the F factor as a plasmid.

F- strains of Escherichia coli
A) do not have an F factor.
B) have the F factor as a plasmid.
C) have an integrated F factor.
D) transfer the F factor to other strains at a high frequency.

A) do not have an F factor.

All Hfr strains integrate into the chromosome at
A) the same locus.
B) several specific sites.
C) the same locus most of the time, although there may be some variation.

D) loci that cannot be accurately determined.

B) several specific sites.

Transposition is a(n)
A) homologous recombination event.
B) analogous recombination event.
C) site-specific recombination event.

D) general recombination event.

C) site-specific recombination event.

The enzyme transposase may be coded for by insertion sequences on a

A) chromosome.
B) phage.
C) plasmid.

D) chromosome, phage, or plasmid.

D) chromosome, phage, or plasmid.

A ʺpoint mutationʺ refers to mutations involving

A) a base-pair substitution.
B) the gain of a base pair (microinsertion).
C) the deletion of a base pair (microdeletion).

D) a substitution, deletion, or addition of one base-pair.

D) a substitution, deletion, or addition of one base-pair.

A deleterious mutation in recA results in
A) a decrease in specific recombination.
B) a decrease in homologous recombination.
C) an increase in homologous recombination.
D) no change in either general or specific recombination.

B) a decrease in homologous recombination.

The production of a functional gene product by transforming bacteria that lack a lacZ gene with a plasmid containing a lacZ gene is known as
A) complementation.
B) mitosis.

C) transfection.
D) reversion.

A) complementation.

Consider conjugation in Escherichia coli. In which of the following matings would chromosomal genes be transferred most frequently?

A) F+ × F-

B) F- × F-

C) Hfr × F-

D) F+ × F+

C) Hfr × F-

Which of the following features are common to transformation, transduction, and conjugation?

(1) unidirectional transfer of genes
(2) incomplete gene transfer
(3) homologous recombination
(4) meiosis occurring in the recipient
A) 1,2,3
B) 1,2
C) 3,4
D) 1,2,4

A) 1,2,3