Deck 15: Regulation of Gene Expression

Question 1

A lack of which of the following molecules would result in the cell's inability to "turn off" genes?

A)operon
B)inducer
C)promoter
D)corepressor

Answer 1

D

Question 2

What effect does methylation have on DNA?

A)It allows it to be replicated nearly continuously.
B)It allows it to be unwound in preparation for protein synthesis.
C)It makes it transcriptionally inactive.
D)It activates transcription.

Answer 2

C

Question 3

Which of the following environments would most likely lead to the transcription of the lactose operon?

A)There is more glucose in the cell than lactose.
B)The cyclic AMP levels are low.
C)There is glucose but no lactose in the cell.
D)The cyclic AMP and lactose levels are both high within the cell.
E)The cAMP level is high and the lactose level is low.

Answer 3

D

Question 4

Which of the following statements correctly describes the role of general transcription factors in eukaryotes?

A)They are required for the expression of specific protein-encoding genes.
B)They bind to other proteins or to a sequence element within the promoter called the TATA box.
C)They inhibit RNA polymerase binding to the promoter and begin transcribing.
D)They usually lead to a high level of transcription even without additional specific transcription factors.

Question 5

In positive control of several sugar-metabolism-related operons,the cAMP receptor protein (CRP)binds to DNA to stimulate transcription.Which of the following events activates CRP?

A)increase in glucose and increase in cAMP
B)decrease in glucose and increase in cAMP
C)increase in glucose and decrease in cAMP
D)decrease in glucose and increase in repressor

Question 6

Which of the following must occur in order for a repressible operon to be transcribed?

A)A corepressor must be present.
B)RNA polymerase and the active repressor must be present.
C)RNA polymerase must bind to the promoter,and the repressor must be inactive.
D)RNA polymerase cannot be present,and the repressor must be inactive.

Question 7

Which of the following statements correctly describes the role of histone acetylation and DNA methylation in gene regulation?

A)DNA methylation reduces transcription,and histone acetylation promotes transcription.
B)DNA methylation promotes transcription,and histone acetylation reduces transcription.
C)DNA methylation and histone acetylation both promote transcription.
D)DNA methylation and histone acetylation both reduce transcription.

Question 8

A type of mutation in bacteria in the repressor results in a molecule known as a super-repressor because it represses the lac operon permanently.Which of the following processes would occur in such a mutant?

A)The repressor protein cannot bind to the operator.
B)A functional repressor protein is produced.
C)The repressor protein cannot bind the inducer.
D)The lac operon will be transcribed continuously.

Question 9

Altering patterns of gene expression in prokaryotes would most likely contribute to the organism's survival in which of the following ways?

A)organizing gene expression so that genes are expressed in a given order
B)allowing each gene to be expressed an equal number of times
C)allowing the organism to adjust to changes in environmental conditions
D)allowing young organisms to respond differently than more mature organisms

Question 10

Which of the following activities can prokaryotes carry out in response to certain chemical signals?

A)turn off translation of their mRNA
B)alter the level of production of various enzymes
C)increase the number and responsiveness of their ribosomes
D)inactivate their mRNA molecules

Question 11

Which of the following is a protein product of a regulatory gene?

A)operon
B)inducer
C)promoter
D)repressor

Question 12

The tryptophan operon in some bacteria is a repressible operon.Which of the following statements correctly describes this operon?

A)It is permanently active.
B)It is activated only when tryptophan is present in the growth medium.
C)It is activated only when glucose is present in the growth medium.
D)It is deactivated whenever tryptophan is added to the growth medium.

Question 13

When the substrate of a metabolic pathway is present in a bacterial cell,which of the following processes will occur?

A)transcription of the genes in a repressible operon
B)deactivation of the promoter for an operon
C)transcription of the genes in an inducible operon
D)allosteric regulation of an inducer

Question 14

Which of the following events occurs during DNA replication?

A)All methylation of the DNA is lost at the first round of replication.
B)DNA polymerase is blocked by methyl groups,and methylated regions of the genome are therefore left uncopied.
C)Methylation of the DNA is maintained because methylation enzymes act at DNA sites where one strand is already methylated and thus correctly methylate daughter strands after replication.
D)Methylation of the DNA is maintained because DNA polymerase directly incorporates methylated nucleotides into the new strand opposite any methylated nucleotides in the template.

Question 15

Allolactose,an isomer of lactose,is formed in small amounts from lactose.An E.coli cell is presented for the first time with the sugar lactose (containing allolactose)as a potential food source.Which of the following processes occurs when the lactose enters the cell?

A)The repressor protein attaches to the regulator.
B)Allolactose binds to the repressor protein.
C)Allolactose binds to the operator.
D)The repressor protein and allolactose bind to RNA polymerase.
E)Allolactose binds to the inducer.

Question 16

What would be the result of a mutation that deactivates the regulatory gene of a repressible operon in an Escherichia coli cell?

A)continuous transcription of the enzyme-coding gene controlled by that regulator
B)complete inhibition of transcription of the enzyme-coding gene controlled by that regulator
C)irreversible binding of the repressor to the operator
D)inactivation of RNA polymerase by alteration of its active site

Question 17

Which of the following statements correctly describes the role of a molecule that controls a repressible operon?

A)The molecule binds to the promoter region and decreases the affinity of RNA polymerase for the promoter.
B)The molecule binds to the operator region and blocks the attachment of RNA polymerase to the promoter.
C)The molecule increases the production of inactive repressor proteins.
D)The molecule binds to the repressor protein and activates it.

Question 18

Which of the following molecules,when taken up by the cell,binds to the repressor so that the repressor no longer binds to the operator?

A)ubiquitin
B)inducer
C)promoter
D)repressor

Question 19

Which of the following mechanisms is used to coordinate the expression of multiple,related genes in eukaryotic cells?

A)A specific combination of control elements in each gene's enhancer coordinates the simultaneous activation of the genes.
B)The genes share a single common enhancer,which allows appropriate activators to turn on their transcription at the same time.
C)The genes are organized into large operons,allowing them to be transcribed as a single unit.
D)A single repressor is able to turn off several related genes.

Question 20

Most repressor proteins exhibit allosteric properties.Which of the following molecules binds with the repressor to alter its structure?

A)inducer
B)promoter
C)RNA polymerase
D)transcription factor

Question 21

You are given an experimental problem involving control of a gene's expression in the embryo of a particular species.One of your first questions is whether the gene's expression is controlled at the level of transcription or translation.Which of the following experiments might best give you an answer?

A)You explore whether there has been alternative splicing by examining amino acid sequences of very similar proteins.
B)You measure the quantity of the appropriate pre-mRNA in various cell types and find they are all the same.
C)You assess the position and sequence of the promoter and enhancer for this gene.
D)You analyze amino acid production by the cell and find that there is an increase at this stage of embryonic life.

Question 22

Which of the following statements best describes siRNA?

A)a short double-stranded RNA,one of whose strands can block gene expression
B)a double-stranded RNA that is formed by cleavage of hairpin loops in a larger precursor
C)a portion of rRNA that allows it to bind to several ribosomal proteins in forming large or small subunits
D)an RNA sequence that can block the expression of some transposons

Question 23

Among the newly discovered small noncoding RNAs,one type reestablishes methylation patterns during gamete formation and blocks expression of some transposons.
What are these types of RNA called?

A)miRNA
B)piRNA
C)snRNA
D)siRNA

Question 24

In the microarray shown in the figure above,if you were searching for genes whose expression was inhibited by hormone treatment,you would search for sequences spotted on the array that showed what level of fluorescence?

A)none
B)high levels
C)green
D)red

Question 25

Researchers are looking for better treatments for breast cancer.For a particular DNA microarray assay (DNA chip),cDNA has been made from the mRNAs of a dozen patients' breast tumor biopsies.What would the researchers be looking for in this type of assay?

A)a particular gene that is amplified in all or most of the patient samples
B)a pattern of fluorescence that indicates which cells are overproliferating
C)a pattern shared among some or all of the samples that indicates gene expression differing from control samples
D)a group of cDNAs that act differently from those on the rest of the grid

Question 26

Which of the following results can a DNA microarray assay detect or identify?

A)They can identify the function of any gene in a genome.
B)They can be used to introduce entire genomes into bacterial cells.
C)They allow the expression of many or even all of the genes in a genome to be compared at once.
D)They allow physical maps of the genome to be assembled in a very short time.

Question 27

One way scientists hope to use the recent knowledge gained about noncoding RNAs lies with the possibilities for their use in medicine.Of the following scenarios for future research,which would you expect to gain most from RNAs?

A)exploring a way to turn on the expression of introns
B)targeting siRNAs to disable the expression of an allele associated with an autosomal recessive disease
C)targeting siRNAs to disable the expression of an allele associated with an autosomal dominant disease
D)creating organisms that can be useful for pharmaceutical drug design

Question 28

In a genome-wide expression study using a DNA microarray assay,what is each spot used to detect?

A)the fate of proteins produced by a cell
B)the location of a protein produced by a cell
C)the location of a gene within a cell
D)the expression of a specific gene by a cell

Question 29

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.If she moves the regulatory gene (lac I),along with its promoter,to a position some several thousand base pairs away from its normal position,which would you expect to occur?

A)The repressor will no longer be made.
B)The repressor will no longer bind to the operator.
C)The repressor will no longer bind to the inducer.
D)The lac operon will function normally.

Question 30

Which of the following techniques involves reverse transcriptase,PCR amplification,and gel electrophoresis?

A)DNA microarray assays
B)RT-PCR
C)in situ hybridization
D)nucleic acid hybridization

Question 31

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.If she moves the promoter for the lac operon to the region between the beta galactosidase (lacZ)gene and the permease (lacY)gene,which of the following results would be likely?

A)The three genes will be expressed normally.
B)RNA polymerase will no longer transcribe permease.
C)The operon will no longer be inducible.
D)Beta galactosidase will not be produced.

Question 32

Transcription factors in eukaryotes usually have DNA-binding domains as well as other domains that are specific for binding other molecules.In general,which of the following would you expect many of them to be able to bind?

A)repressors
B)protein-based hormones
C)other transcription factors
D)tRNA

Question 33

At the beginning of this century there was a general announcement regarding the sequencing of the human genome and the genomes of many other multicellular eukaryotes.There was surprise expressed by many that the number of protein-coding sequences in the human genome was much smaller than had been expected.Which of the following statements would describe most of the rest of the DNA in the human genome?

A)"junk" DNA that serves no possible purpose
B)rRNA and tRNA coding sequences
C)DNA that is translated directly without being transcribed
D)non-protein-coding DNA that is transcribed into several kinds of small RNAs with biological function

Question 34

Which of the following statements describes one of the functions of the protein called ubiquitin?

A)It attaches to proteins that are marked for destruction in the cell.
B)It assists in the removal of introns from a eukaryotic pre-mRNA.
C)It initiates the formation of a transcription complex.
D)It adds the 3' and 5' caps to eukaryotic pre-mRNA.

Question 35

A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture.In one set of experiments she succeeded in decreasing methylation of histone tails.Which of the following results would she most likely see?

A)increased chromatin condensation
B)decreased chromatin condensation
C)activation of histone tails for enzymatic function
D)decreased binding of transcription factors

Question 36

Suppose an experimenter becomes proficient with a technique that allows her to move DNA sequences within a prokaryotic genome.If she moves the operator to the far end of the operon,past the transacetylase (lacA)gene,which of the following results would likely occur when the cell is exposed to lactose?

A)The inducer will no longer bind to the repressor.
B)The repressor will no longer bind to the operator.
C)The operon will never be transcribed.
D)The three genes of the operon will be transcribed continuously.

Question 37

Since Watson and Crick described the structure of DNA in 1953,which of the following statements might best explain why the function of small RNAs is still being explained?

A)As RNAs have evolved since that time,they have taken on new functions.
B)Watson and Crick described DNA but did not predict any function for RNA.
C)The functions of small RNAs could not be approached until the entire human genome was sequenced.
D)Changes in technology as well as our ability to determine how much of the DNA is expressed have now made this possible.

Question 38

Gene expression can be blocked by a process called RNA interference.Which of the following molecules is involved in this process?

A)siRNAs
B)mRNA
C)rRNAs
D)tRNA

Question 39

Which of the following processes do steroid hormones carry out to produce their effects?

A)They activate key enzymes in metabolic pathways.
B)They activate translation of certain mRNAs.
C)They promote the breakdown of specific mRNAs.
D)They bind to receptors inside the cell and promote transcription of specific genes.

Question 40

Gene expression might be altered based on post-transcriptional processing in eukaryotes rather than prokaryotes.Which of the following statements describes this difference?

A)Eukaryotic mRNAs get 5' caps and 3' tails.
B)Prokaryotic genes are expressed as mRNA,which is more stable in the cell.
C)Eukaryotic exons may be spliced in alternative patterns.
D)Prokaryotes use ribosomes of different structure and size.

Question 41

A researcher introduces double-stranded RNA into a culture of mammalian cells.The double-stranded RNA corresponds to a region of a protein-coding gene of interest.How may the introduced RNA affect gene expression in these cells?

A)The overall rate of translation in the cell may be significantly reduced.
B)The overall rate of transcription in the cell may be significantly reduced.
C)The overall rate of transcription in the cell may be significantly increased.
D)The amount of protein produced by the target gene may be significantly reduced.

Question 42

Which statement about DNA in one of your brain cells is true?

A)Most of the DNA codes for protein.
B)The majority of genes are likely to be transcribed.
C)It is the same as the DNA in one of your liver cells.
D)Many genes are grouped into operon-like clusters.

Question 43

Which of the following would not be true of cDNA produced using human brain tissue as the starting material?

A)It could be amplified by the polymerase chain reaction.
B)It was produced from pre-mRNA using reverse transcriptase.
C)It could be labeled and used as a probe to detect genes expressed in the brain.
D)It lacks the introns of the pre-mRNA.

Question 44

If a particular operon encodes enzymes for making an essential amino acid and is regulated like the trp operon,then

A)the amino acid inactivates the repressor.
B)the repressor is active in the absence of the amino acid.
C)the amino acid acts as a corepressor.
D)the amino acid turns on transcription of the operon.

Question 45

The functioning of enhancers is an example of

A)a eukaryotic equivalent of prokaryotic promoter functioning.
B)transcriptional control of gene expression.
C)the stimulation of translation by initiation factors.
D)post-translational control that activates certain proteins.

Question 46

A researcher found a method she could use to manipulate and quantify acetylation in embryonic cells in culture.In one set of experiments using this procedure in Drosophila,she was readily successful in increasing acetylation of amino acids in histone tails.Which of the following results would she most likely see?

A)increased chromatin condensation
B)decreased chromatin condensation
C)activation of histone tails for enzymatic function
D)decreased binding of transcription factors

Question 47

What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?

A)irreversible binding of the repressor to the promoter
B)reduced transcription of the operon's genes
C)buildup of a substrate for the pathway controlled by the operon
D)continuous transcription of the operon's genes

Question 48

Which of the following is an example of post-transcriptional control of gene expression?

A)the addition of methyl groups to cytosine bases of DNA
B)the binding of transcription factors to a promoter
C)the removal of introns and alternative splicing of exons
D)the binding of RNA polymerase to transcription factors