Deck 20: The Regulation of Gene Expression

Question 1

You are examining a bacterial enzyme associated with glycolysis.You would expect expression of the enzyme to be

A)amplified when glucose is depleted.
B)induced by glucose.
C)repressed by glucose.
D)induced when ATP concentrations in the cell are high.
E)controlled by a riboswitch.

Answer 1

B

Question 2

The situation in which an active regulatory protein "turns on" gene expression is an example of

A)feedback inhibition.
B)positive control.
C)negative control.
D)constitutive gene elements.
E)a mutation.

Answer 2

B

Question 3

The chromosome of a bacterial cell possesses the following genotype with regard to the lac operon: I⁻O⁺Z⁺Y⁻A⁻.This bacterial cell would

A)make β-galactosidase in the presence of lactose.
B)make β-galactosidase independently of lactose.
C)make β-galactosidase and galactoside permease in the presence of lactose.
D)make transacetylase in the presence of lactose.
E)make no lac gene products.

Answer 3

B

Question 4

The accompanying graph shows a growth curve of E.coli growing in a defined medium containing equal molar amounts of glucose and lactose. Based on your knowledge of the regulation of the lac operon,the best explanation of these results is that

A)early on,due to the presence of lactose,the bacteria use the lac operon.Glucose is used later.
B)the bacteria use both sugars simultaneously.
C)the presence of glucose causes the formation of cAMP catabolic repressor protein (CRP)complexes,which shut down the lac operon until the glucose is used up.
D)glucose is used first.Once glucose becomes limiting,intracellular cAMP increases,forming cAMP-CRP complexes that activate the lac operon to use lactose.
E)early on the glucose binds to the repressor protein lacI and shuts down the lac operon.

Question 5

Which of the following processes is/are associated with the modification of histone proteins in vivo?

A)acetylation
B)alkylation
C)methylation
D)transhydroxylation
E)acetylation and methylation

Question 6

Which of the following is an example of translational regulation?

A)protein degradation
B)DNA splicing
C)protein folding
D)mRNA degradation
E)DNA methylation

Question 7

How many Barr bodies would you expect to see in the cells of an individuals with sex chromosome complement XXX?

A)0
B)1
C)2
D)3
E)4

Question 8

In eukaryotes,gene amplification is ________ and may occur when ________.

A)the creation of multiple copies of the same gene; a large amount of the gene product is required for cell function
B)a sudden increase in transcription of a gene; a large amount of the gene product is required for cell function
C)a sudden increase in translation of a mRNA; a large amount of the gene product is required for cell function
D)the creation of multiple copies of the same gene; transcription and translation are suppressed
E)a sudden increase in transcription of a gene; translation is suppressed

Question 9

The observed "puffs" in the polytene chromosomes of Drosophila are sites of

A)attenuation.
B)condensation.
C)induction.
D)transcription.
E)translation.

Question 10

You are examining an enzyme associated with cysteine biosynthesis.You would expect expression of the enzyme to be

A)amplified when cysteine concentrations are high.
B)induced by cysteine.
C)repressed by cysteine.
D)high when ATP concentrations in the cell are low.
E)controlled by a riboswitch.

Question 11

The situation in which an active regulatory protein "turns off" gene expression is an example of

A)a mutation.
B)positive control.
C)negative control.
D)constitutive gene elements.
E)unique regulation.

Question 12

In E.coli cell with the genotype lac $O ^ { c }$ $Z ^ { + }$ $Y ^ { - }$ $A ^ { - }$ would make which of the following protein products and in what manner?

A)LacZ,induced
B)LacZ and Lac A,induced
C)LacY,constitutive
D)LacZ,constitutive
E)LacZ and LacA,constitutive

Question 13

The trp operon in E.coli is regulated in such a manner as to allow expression of the genes only when cellular levels of tryptophan are low.When tryptophan levels are adequate,the secondary structure of the mRNA halts translation.This form of regulation is known as

A)attenuation.
B)transcriptional regulation.
C)positive regulatory control.
D)allosteric inhibition.
E)induction.

Question 14

Effector molecules

A)are associated with the induction of enzyme synthesis.
B)are associated with the repression of enzyme synthesis.
C)induce conformational changes.
D)are often small organic molecules.
E)All of these are true.

Question 15

Comparison of gene expression in different human tissues using the nuclear run-on transcription assay illustrates that

A)differences in protein production are mainly due to post-transcriptional mechanisms.
B)few differences in protein production are detected between tissues.
C)differences in protein production are mainly due to differential gene transcription.
D)differences in protein production are not due to differential gene transcription.
E)few differences in RNA production are detected between different tissues; thus differential protein production is mainly due to post-transcriptional mechanisms.

Question 16

Genes associated with embryonic development are known as

A)homologous genes.
B)sigma factors.
C)heterologous genes.
D)hopanoids.
E)homeotic genes.

Question 17

Sigma (σ)factors can regulate the initiation of transcription.Which of the following is not an example of σ regulation?

A)Some σ factors recognize promoters for genes whose products are necessary when the organism is under stress,such as heat shock.
B)Some σ factors recognize promoters for genes whose products are necessary for nitrogen utilization.
C)Bacteriophages may code for specific σ factors that bind the core RNA polymerase and result in recognition of viral promoters.
D)Many σ factors regulate genes associated with embryonic development in eukaryotes.
E)UV irradiation can trigger the use of alternative σ factors.

Question 18

A lacO^c mutant would

A)never express lac structural genes.
B)constitutively express the lac structural genes.
C)not bind to lacI.
D)use glucose before using lactose as a carbon and energy source.
E)not bind to lacI and never express lac structural genes.

Question 19

A lac ^I− mutant would

A)express lacZYA constitutively.
B)not induce lacZYA in the presence of lactose.
C)not have β-galactosidase activity.
D)not transport lactose into the cell effectively.
E)not metabolize lactose.

Question 20

A male is tested for cellular abnormalities.The technician notes that there are two Barr bodies present within each of the patient's cells.This indicates that his chromosome complement is most likely

A)XY.
B)XO.
C)XXX.
D)XXY.
E)XXXY.

Question 21

You are working with a gene associated with an essential pathway that is necessary at two time points in an organism's lifetime.With regard to gene regulation,you would expect the gene to be

A)constitutive.
B)associated with response to distinct events.
C)induced by particular signals.
D)repressed by particular signals.
E)associated with response to distinct events through induction and repression signals.

Question 22

Genes that are expressed only when needed are

A)unregulated.
B)mutations.
C)inducible.
D)constitutive.
E)anabolic.

Question 23

You are studying a biochemical pathway.Preliminary results suggest that this pathway is subject to end-product repression.This pathway is therefore most likely to be a(n)________ pathway.

A)anabolic
B)catabolic
C)constitutive
D)induced
E)unregulated

Question 24

Which of the following does not apply to eukaryotic gene regulation?

A)gene regulation by attenuation
B)regulation as a result of compartmentalization
C)mRNA degradation (turnover)
D)protein degradation (turnover)
E)protein folding

Question 25

Small molecules that bind directly to mRNAs and effect transcription or translation are binding to regions of the mRNA known as

A)Shine-Dalgarno sequences.
B)operator regions.
C)riboswitches.
D)ribozymes.
E)allosteric sites.

Question 26

Gene knockdown via RNAi relies on the ability of eukaryotic cells to

A)degrade target mRNAs that are complementary to introduced dsRNA.
B)induce microRNA expression under particular conditions.
C)preferentially degrade mutated mRNAs.
D)inhibit transcription of sets of genes based on the presence of distal control elements.
E)preferentially degrade mutated mRNAs by inducing microRNA expression under particular conditions.

Question 27

Which of the following DNA sequence elements coordinates the expression of nonadjacent genes in eukaryotes?

A)activation domains
B)response elements
C)epigenetic sequences
D)coactivating elements
E)DNase I hypersensitive sites

Question 28

A eukaryotic gene is observed to make multiple forms of a protein.How can one eukaryotic gene produce multiple products in the same cell?

A)Alternative splicing sites can lead to the production of two different mature mRNAs from the same gene,resulting in slightly different proteins.
B)Epigenetic changes can change the sequence of amino acids in a protein.
C)Translation rates can affect the length of the polypeptide made from the same mRNA.
D)Silencer genetic elements can cause early termination of transcription,leading to the production of multiple mature mRNAs from the same gene.
E)One gene equals one protein,so this observation must be incorrect.

Question 29

Within a genome,an enhancer may be located

A)upstream of the gene enhanced.
B)downstream of the gene enhanced.
C)within the introns of other genes.
D)proximal to the gene enhanced.
E)upstream or downstream of the gene enhanced,even within the introns of other genes.

Question 30

The iron-response element (IRE)is a(n)

A)insulator element that binds IRE-binding protein in the absence of iron.
B)transcriptional promoter that directly binds iron to prevent transcription of nearby genes.
C)long noncoding RNA that binds iron and regulates transcription of multiple genes.
D)sequence in the 5ʹ untranslated region of mRNA that forms a hairpin loop,preventing translation of the mRNA by binding to IRE-binding protein in the absence of iron.
E)example of a prokaryotic riboswitch that causes early termination of transcription in the presence of iron.

Question 31

In eukaryotes,post-transcriptional control of gene regulation may involve

A)alternative mRNA splicing.
B)control of nuclear export of mRNAs to the cytoplasm.
C)differential mRNA degradation.
D)gene amplification and methylation.
E)alternative mRNA splicing,control of nuclear export of mRNAs to the cytoplasm,and differential mRNA degradation.

Question 32

Genes that are always "turned on" in a cell are referred to as

A)regulated genes.
B)mutations.
C)inducible.
D)constitutive.
E)catabolic.

Question 33

P bodies play an important role in

A)post-transcriptional regulation in eukaryotic cells.
B)epigenetic regulation in eukaryotic cells.
C)operon regulation in prokaryotic cells.
D)chromosome inactivation.
E)epigenetic and post-transcriptional regulation in eukaryotic cells.

Question 34

Protein phosphorylation,protein folding,and proteolytic cleavage are all examples of

A)post-transcriptional control of gene expression and activity.
B)epigenetic control of inheritance.
C)repression of gene expression.
D)induction of gene expression.
E)post-translational control of gene expression and activity.

Question 35

One mechanism that may lead to novel disease treatment involves ________,which hinders the translation of specific mRNAs.

A)siRNA
B)tRNA
C)P bodies
D)macro-RNAs
E)rRNA

Question 36

Which of the following is not a structural motif associated with transcriptional regulation?

A)CpG motif
B)helix-turn-helix
C)zinc finger
D)leucine zipper
E)helix-loop-helix

Question 37

A DNA element that decreases transcription of a gene from a vast distance is known as a(n)

A)insulator.
B)TATA box.
C)regulator.
D)proximal control element.
E)silencer.

Question 38

DNA rearrangements in eukaryotes can

A)cause chromosome puffs.
B)enhance production of the certain gene products.
C)increase the diversity of possible gene products from a limited number of genes.
D)allow for epigenetic regulation.
E)enhance production of the certain gene products and increase the diversity of possible gene products from a limited number of genes.

Question 39

The genes of the lac operon code for proteins associated with lactose metabolism.Which of the lac gene products is associated with transport of lactose into the cell?

A)β-galactosidase
B)transacetylase
C)galactoside permease
D)β-lactase
E)lactose translocase

Question 40

In eukaryotic cells,which of the following genetic elements can prevent the increase in gene expression that results from the presence of an enhancer sequence?

A)repressor
B)silencer
C)cofactor
D)insulator
E)sigma factor

Question 41

________ is the term given to the process by which cells delete genes when the gene products are no longer required,as occurs in mammalian red blood cells.

Question 42

What is the difference between trans- and cis-acting regulatory factors? Design an experiment that allows you to prove your answer to the question.

Question 43

The regulation of eukaryotic gene expression is ________,allowing a relatively small number of different DNA control elements and transcription factors to establish highly specific and precisely controlled patterns of gene expression by acting in different combinations in different cell types.

Question 44

________ allows mammalian cells to regulate gene expression and produce multiple mRNAs from the same pre-mRNA.

Question 45

Cloning eukaryotic organisms involves the transfer of a ________ into a cell that lacks one to direct the development of a new organism.

Question 46

Inactivated X chromosomes form dark spots in the nuclei of stained cells known as ________.

Question 47

An individual whose sex chromosome complement is XXY has ________ Barr body/bodies in their cells.

Question 48

A bacterium has the following lac operon genes located on the chromosome: I⁺P⁻Z⁻Y⁻A^+. On a plasmid,this same bacterial cell has the lac genes I⁻P⁺Z⁻Y⁺A^−. Which protein products will be made from lac genes in response to the presence of lactose? What type of protein expression (induced or constitutive)will there be for each protein that is made?

Question 49

________ of cytosine bases in mammals causes decreased accessibility of DNA to the transcriptional machinery,resulting in transcriptional repression.

Question 50

In order to activate genes associated with lactose metabolism,the levels of cAMP must be ________ in a bacterial cell.

Question 51

Iron-response elements are part of the untranslated regions of mRNA and regulate gene expression through ________ control.

Question 52

________ is the process of RNA-mediated inhibition of gene expression.

Question 53

Inherited changes in gene expression that are not the result of changes to the gene sequence itself are known as ________ changes.

Question 54

Addition of the short polypeptide ________ targets proteins for destruction.

Question 55

The nucleus of a differentiated cell contains all of the genetic information necessary to direct the development of an entire organism.This nucleus is therefore said to be ________.

Question 56

The concentration of iron in a cell is an important regulator of gene expression.Explain two mechanisms through which iron concentration regulates gene expression in mammalian cells.