Deck 12: Gene Expression

Question 1

DNA controls

A) in which tissues genes are expressed.
B) when genes are expressed.
C) for how long genes are expressed.
D) gene expression in response to the environment.
E) All of the answers are correct.

Answer 1

All of the answers are correct.

Question 2

Gene repression is important so that

A) genes cannot be turned off.
B) organisms do not waste energy expressing genes that are not needed all the time.
C) organisms can respond to their environment.
D) genes cannot be turned off and organisms do not waste energy expressing genes that are not needed all the time.
E) organisms do not waste energy expressing genes that are not needed all the time and organisms can respond to their environment.

Answer 2

organisms do not waste energy expressing genes that are not needed all the time and organisms can respond to their environment.

Question 3

In the regulation of gene expression, negative regulation

A) induces transcription of a gene in response to environmental conditions.
B) alters the DNA sequence to contain a nonsense mutation.
C) represses transcription of a gene in response to environmental conditions.
D) increases the production of regulatory proteins.
E) causes a gene to be expressed constitutively.

Answer 3

represses transcription of a gene in response to environmental conditions.

Question 4

Genes involved in the metabolism of an energy source are usually

A) positively regulated.
B) negatively regulated.
C) not regulated.
D) expressed constitutively.
E) directly inhibited by ATP.

Question 5

Genes involved in the synthesis of amino acids are usually only expressed when the amino acids are running out. This is an example of

A) positive regulation.
B) negative regulation.
C) no regulation.
D) direct inhibition of transcription by specific amino acids.
E) constitutive expression.

Question 6

A unicellular protist lives in the gut of an insect that eats wood. The protist gains its energy by first breaking the cellulose into sucrose, which it can use. The insect is brought into a lab and fed on a starch solution, which induces a different set of metabolic genes. You would expect the protist to

A) starve.
B) switch off genes for manufacturing cellulases.
C) switch off genes for the degradation of sucrose.
D) manufacture cellulose.
E) induce genes to manufacture cellulase.

Question 7

Regulation of gene expression

A) can only occur at the level of transcription of mRNA from the DNA code.
B) occurs because of the rate at which translation is carried out.
C) occurs by stabilising the mRNA for the gene.
D) happens at numerous levels, including transcriptional and translational control.
E) does not include alteration to the protein products of translation.

Question 8

Which of the following statements about protein synthesis and regulation of genes is CORRECT?

A) Transcription and translation require an energy input.
B) Protein modification is the most common means for the control of gene expression.
C) All cells can induce or repress genes in response to environmental cues.
D) Bacteria continuously manufacture a set of enzymes such that they can utilise most commonly found substrates.
E) mRNA is produced at a constant rate.

Question 9

Transcriptional control is of great importance in prokaryotes, because

A) transcription and translation are linked.
B) few prokaryotic mRNAs are subject to translational control.
C) their genes are expressed a constitutive level.
D) prokaryotic proteins do not undergo any changes after translation.
E) prokaryotes undergo rapid environmental changes and are required to adapt.

Question 10

Which of the following statements about promoters in prokaryotic genes is CORRECT?

A) Promoters are adjacent to the 3' end of the transcription unit.
B) A promoter is the site of binding DNA polymerase prior to the initiation of transcription.
C) Promoters are adjacent to the operon, the site of binding of specific regulatory proteins.
D) Promoters are not involved in the regulation of gene expression.
E) None of the answers are correct.

Question 11

In the lac operon of E. coli

A) the presence of $\beta$ -galactosidase stimulates transcription of mRNA.
B) lacO is trans-acting.
C) lacI produces a protein inducer.
D) the presence of lactose induces expression of the lac genes.
E) All of the answers are correct.

Question 12

In the lac operon of E. coli, if the lacI region was moved to a different section of the chromosome, but was otherwise unchanged, the most likely result would be that

A) the repressor protein would not be synthesised, so expression of the lac operon would become constitutive.
B) the repressor protein would always be synthesised, so expression of the lac operon would always be repressed.
C) the repressor protein would exert its normal effect on the expression of the lac operon because the lacI gene can act in trans.
D) expression of the lac operon would depend on different repressors, depending on where the lacI was integrated into the chromosome.
E) expression of the lac operon would remain normal because the lacI gene is not involved in the regulation of the lac operon.

Question 13

A mutation occurs in the operator region of the lac operon of E. coli, and the repressor protein is unable to bind. Which of the following would occur?

A) Synthesis of the repressor protein would stop.
B) Lactose would not enter the cell.
C) The promoter region would be transcribed.
D) The genes from the lac operon would not be transcribed.
E) Structural genes would be continuously transcribed.

Question 14

In the regulation of the lac operon in Escherichia coli, allolactose

A) is one of the products of lactose metabolism by the cell.
B) has an allosteric interaction with the repressor protein, which makes the repressor protein unable to bind to the operator region.
C) results in an increased rate of transcription of the lacZ, lacY and lacA genes.
D) All of the answers are correct.
E) None of the answers are correct.

Question 15

In the regulation of the lac operon in Escherichia coli, cyclic AMP

A) is a small metabolite that binds with lactose to increase transcription of the lac operon.
B) increases in concentration when glucose is present in the cell.
C) is produced from glucose to inhibit the binding of RNA polymerase to the lac operon.
D) is involved in the positive regulation of the lac operon via its allosteric interaction with the catabolite activator protein.
E) prevents the RNA polymerase from binding to the promoter region via its allosteric interaction with the catabolite activator protein.

Question 16

In the regulation of the lac operon in Escherichia coli, if both glucose and lactose were available energy sources for the cell, you would NOT expect that

A) the presence of glucose would result in a decreased concentration of cAMP in the cell.
B) the lac operon would not undergo an increase in transcription.
C) glucose would be the favoured energy source for the cell.
D) the catabolite-binding protein would bind cAMP to inhibit the expression of the lac operon.
E) RNA polymerase would bind more efficiently to the promoter region of the lac operon.

Question 17

The main difference between the mode of regulation of the lac and trp operons in Escherichia coli is that

A) the presence of tryptophan leads to the repression of the trp operon whereas the presence of lactose leads to the expression of the lac operon.
B) the presence of tryptophan leads to the expression of the trp operon whereas the presence of lactose leads to the repression of the lac operon.
C) the lac operon is constitutively expressed whereas the trp operon is regulated.
D) there are no major differences in the mode of regulation, just in the products of the genes involved.
E) the lac gene consists of a promoter region while the trp gene only contains a cis-acting operator sequence.

Question 18

If the operator region of the trp operon in Escherichia coli were moved to a different section of the chromosome, but was otherwise unchanged, the most likely result would be that

A) the presence of tryptophan in the cell would no longer repress expression of the trp operon.
B) the tryptophan-trp repressor complex would still bind to the operator region.
C) the trp repressor protein would always bind to the operator region.
D) the presence of tryptophan in the cell would no longer repress expression of the trp operon and the tryptophan-trp repressor complex would still bind to the operator region.
E) the tryptophan-trp repressor complex would still bind to the operator region and the trp repressor protein would always bind to the operator region.

Question 19

DNA-binding regulatory proteins or transcription factors

A) are proteins that help to regulate transcription in eukaryotes.
B) bind to enhancers to stimulate transcription.
C) bind to silencers to suppress transcription.
D) can vary from tissue to tissue.
E) All of the answers are correct.

Question 20

Regulation of the genes responsible for galactose metabolism in Saccharomyces cerevisiae

A) only works because the five genes involved are cistronic.
B) involves the constitutively expressed GAL4 and GAL80 genes.
C) requires GAL4, a positive regulator, mutations in which result in constitutive expression of the GAL genes.
D) All of the answers are correct.
E) None of the answers are correct.

Question 21

The Gal4p protein can simultaneously regulate the five genes involved in galactose metabolism in Saccharomyces cerevisiae, despite binding to a specific 17-base pair upstream activator sequence (UAS), because

A) it binds to the UAS of the first gene, triggering a regulatory gene cascade that quickly increases transcription of the other four genes.
B) the five genes are grouped into a single cistron and are regulated by one UAS.
C) each of the five genes has the same UAS.
D) each of the five genes has its own UAS to bind the Gal4p-Gal80p complex to initiate transcription.
E) it is not the binding of the Gal4p protein to the UAS that is involved in regulation, but the protein synthesised from the UAS.

Question 22

In eukaryotic genes

A) multiple promoter elements are found.
B) transcription is initiated solely by the initiation complex.
C) adaptor molecules initiate transcription.
D) the same enhancers drive expression of the same gene in different tissues.
E) expression is not influenced by chemical signals.

Question 23

An activator-binding site that is located on the same chromosome as the gene it affects is called

A) a monosome.
B) an enhancer.
C) an adaptor molecule.
D) a promoter.
E) an operator.

Question 24

Which of the following statements about gene expression in different cells is CORRECT?

A) The same gene can show different patterns of expression because its position on the chromosome varies between different cells.
B) The same gene can show different patterns because different transcription factors, enhancers and silencers may be present in different cells.
C) Gene expression varies between cells because different cells contain different genes.
D) The same gene can show different expression in different cells when the gene promoter region is different.
E) If the same gene is found in different cells, it will probably show the same pattern of expression.

Question 25

The addition of acetyl groups to histones

A) makes the histones less positively charged.
B) reduces the strength of the ionic bond between histones and DNA.
C) can be a way for enhancer-binding complexes that activate transcription to exert their regulatory effect.
D) plays a critical role in eukaryote gene expression.
E) All of the answers are correct.

Question 26

If a protein repression complex contained a faulty enzyme that could no longer remove acetyl groups from histones, the most likely outcome would be that

A) gene expression would decrease because RNA polymerase would be unable to bind to the promoter region.
B) gene expression would neither increase nor decrease because the acetylation of histones is not involved in the regulation of gene expression.
C) DNA would not be able to be expressed because of the formation of tightly bound nucleosomes.
D) the protein repressor complex would be degraded by endonucleases.
E) gene expression would become constitutive.

Question 27

Eukaryotic genes

A) are monocistronic.
B) code for a single polypeptide.
C) are usually regulated by only one factor.
D) are monocistronic and code for a single polypeptide.
E) are monocistronic and are usually regulated by only one factor.

Question 28

A regulatory cascade of gene expression is when

A) the activation of one gene in turn regulates the expression of other genes, which may in turn regulate the expression of even more genes.
B) an enhancer acts on more than one gene.
C) a gene is constitutively expressed.
D) the same gene in different cells show a different expression pattern.
E) protein repression complexes do not contain enzymes that remove acetyl groups.

Question 29

MicroRNAs

A) are a recently discovered mode of regulation of gene expression in Caenorhabditis elegans.
B) are the RNA product of some regulatory genes.
C) can bind to target mRNAs, blocking translation.
D) are not translated into proteins.
E) All of the answers are correct.

Question 30

If a regulatory gene that produced microRNAs had a mutation, the resulting microRNA would

A) remain the same if the mutation was a nonsense mutation.
B) show lower efficacy if the mutation was a missense mutation that was not removed during post-translational processing.
C) show the same efficacy if the mutation was a missense mutation, but was removed during post-transcriptional processing.
D) remain the same if the mutation was a nonsense mutation and show the same efficacy if the mutation was a missense mutation, but was removed during post-transcriptional processing.
E) show lower efficacy if the mutation was a missense mutation that was not removed during post-translational processing and show the same efficacy if the mutation was a missense mutation, but was removed during post-transcriptional processing.

Question 31

Which of the following is NOT a control mechanism utilised by eukaryote cells?

A) Stability of mRNA.
B) Blockage of transcription.
C) The lac operon.
D) Rate of enzyme destruction.
E) Production of microRNA.

Question 32

Regulation of gene expression is essential to maintain cellular homeostasis. Control of gene expression may be achieved by

A) transcription factors which regulate which genes are transcribed in response to the environment.
B) mRNA stability may change and so the amount of protein from a specific gene is changed.
C) the rate of translation of mRNA into a protein may change.
D) a change in the rate of protein degradation by lysosomes.
E) All of the answers are means by which gene expression is controlled.

Question 33

A zinc finger DNA binding domain is

A) the promoter for a zinc-containing enzyme.
B) a DNA sequence which interacts with zinc to enhance the action of trans-acting control proteins which regulate gene transcription.
C) a double stranded region of DNA which is activated by zinc.
D) a DNA sequence which binds regulatory proteins found in eukaryotes.
E) a helix-loop-helix structure in the linear DNA.

Question 34

Regulation of galactose-metabolising enzymes is achieved by

A) the dissociation of the Gal4p-Gal80p complex by galactose to allow Gal80p to dissociate from the DNA binding site and stimulate transcription.
B) a protein Gal80p binds to Gal4p and stimulates transcription by preventing Gal4p binding to the regulatory domain of the GAL4 gene.
C) a protein Gal80p binds to the regulatory domain of the GAL4 gene and inhibits transcription.
D) an upstream activator sequence binds the activating protein Gal80p and stimulates transcription.
E) an upstream activator sequence binds an activator protein (Gal4p) to accelerate gene transcription.

Question 35

The wrapping of DNA into nucleosomes hinders transcription by RNA polymerase. To allow transcription

A) RNA polymerase in eukaryotes contains an exonuclease activity which allows the enzyme to transcribe DNA in nucleosomes.
B) activation complexes often contain enzymes that remove acetyl groups from histones.
C) acetyl groups are added to histone proteins, making them less positively charges and reducing the strength with which they bind to DNA.
D) enhancer-binding proteins contain a protease to degrade histone proteins and make the DNA more accessable.
E) a regulatory cascade ensures that transcription is coordinately regulated with the first protein product being an enzyme to remove histones from DNA.

Question 36

In the presence of glucose, the lac operon

A) is induced.
B) is inhibited.
C) the effect of glucose is dependent on the presence or absence of lactose.
D) the catabolite activator protein (CAP) binds glucose and expression is inhibited.
E) glucose has no effect on the lac operon which is specific for lactose metabolism.

Question 37

Some genes are expressed at constant levels (constitutive) whereas others are expressed at different levels in response to stimuli (differential). What kind of expression would you expect a gene to have if it were involved in the biosynthesis of actin, a component of the cytoskeleton?

A) It could be either constitutive or differential depending on the organism involved.
B) Differential, as actin is required in all cells at a constant, basal level.
C) Differential, as the cytoskeleton is only required in some cells at some developmental stages.
D) Constitutive, as actin filaments are required in all eukaryotic cells in many important processes including cellular structure.
E) Constitutive, as actin expression is responsive to external stimulants.

Question 38

Which of the following is NOT a control point for gene expression

A) Transcript stability
B) Transcript modification
C) Protein stability
D) Protein modification
E) Transcription

Question 39

You are attending a lecture in which the speaker talks about a region of DNA that includes a transcribed region as well as transcriptional regulatory sequences. Such a region must include which individual sequences?

A) Promoter and operator
B) Promoter, operon, ORF
C) Promoter, TATA box
D) Promoter and terminator only
E) ORF, operon, terminator

Question 40

In eukaryotes, DNA binding domains specifically interact with which gene control regions?

A) Polycistronic domains
B) Enhancers only
C) Enhancers or silencers
D) Silencers only
E) 3' untranslated region

Question 41

You are analysing a polymerase enzyme in the laboratory and discover that it cannot initiate transcription on its own. Based on this result, indicate which polymerase this is from the options provided and whether it is from a eukaryote or prokaryote.

A) Prokaryotic DNA polymerase
B) It could be any prokaryotic polymerase
C) Prokaryotic RNA polymerase
D) Eukaryotic RNA polymerase III
E) Eukaryotic RNA polymerase II

Question 42

The transcription of a gene in-vitro is activated by protein A. This activation is repressed when protein B is present which is coded for on a different chromosome. Before protein B is added, protein A can be isolated from the reaction mixture, but when protein B is also present, only a much larger protein is able to be isolated. What is the explanation for this observation?

A) The cis-acting protein B is a repressor that binds to protein A, preventing it from binding to the activation sequence.
B) The cis-acting protein B is binding to the activation sequence, preventing protein A from being able to access and bind to the target sequence.
C) Chromatin remodelling is preventing protein A and/or B from binding to the activation sequence.
D) The trans-acting protein B is a repressor that binds to protein A, preventing it from binding to the activation sequence.
E) The trans-acting protein B is binding to the activation sequence, preventing protein A from being able to access and bind to the target sequence.

Question 43

In what ways do enhancers and silencers involved in eukaryotic transcription differ from prokaryotic regulatory elements?

A) Unlike eukaryotic elements, prokaryotic elements can be in any particular orientation relative to the promoter.
B) Eukaryotic elements can be varying distances from the promoter, prokaryotic elements cannot.
C) Prokaryotic and eukaryotic regulatory elements do not differ: they are the same in location, form and function.
D) Prokaryotic elements can be found within introns, whereas eukaryotic elements cannot.
E) Prokaryotic elements can 'loop', allowing them to bind to promoters. Due to the complexity of eukaryotic chromosomes, looping is not possible.

Question 44

RNA interference (RNAi) is a process whereby

A) RNA that has the same sequence as an introduced short piece of single stranded RNA is inhibited.
B) RNA is degraded (or interfered with) on a systemic level by any non-specific causal agent.
C) RNA that has the same sequence as an introduced short piece of double stranded RNA is inhibited.
D) a rogue sequence of RNA is formed by an intron creating a new ORF which inhibits (interferes with) general RNA synthesis by creating excess transcripts.
E) a short RNA sequence binds to ribosomes, preventing other transcripts from being processed and thus interfering with RNA processing.

Question 45

Which of the following statements about the function of the Dicer RNA endonuclease complex is INCORRECT?

A) It processes pre-miRNA.
B) It processes introduced double stranded RNA.
C) It processes pre-miRNA and introduced double stranded RNA.
D) It creates double stranded RNAs 25-30 nucleotides in length.
E) It creates siRNAs that do not bind with the RISC complex.