Deck 18: Control of Gene Expression

Question 1

If a researcher 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 most likely?

A) The three genes of the lac operon will be expressed normally.
B) RNA polymerase will no longer transcribe permease.
C) The operon will still transcribe the lacZ and lacY genes, but the mRNA will not be translated.
D) Beta galactosidase will not be produced.

Answer 1

D

Question 2

Under what conditions does the trp repressor block transcription of the trp operon?

A) when the repressor binds to the inducer
B) when the repressor binds to tryptophan
C) when the repressor is not bound to RNA polymerase
D) when the repressor is not bound to the operator

Answer 2

B

Question 3

A rise in extracellular glucose results in which of the following changes at the lac operon?

A) RNA polymerase binds the lac promoter with greater affinity
B) cAMP receptor protein (CRP) detaches from the lac promoter
C) lac repressor is allosterically inactivated
D) lac operator binds inducer with greater affinity

Answer 3

B

Question 4

How does breakdown of glucose inhibit transcription of the lac operon?

A) by strengthening the binding of the repressor to the operator
B) by weakening the binding of the repressor to the operator
C) by inhibiting RNA polymerase from opening the strands of DNA to initiate transcription
D) by reducing the levels of intracellular cAMP

Question 5

If a researcher moves the repressor gene (lacI) and its promoter, to a position at some several thousand base pairs away from its normal position, which of the following describes the most likely effect on the lac operon?

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

Question 6

Which of the following conditions is most likely to result in transcription of the lac operon?

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

Question 7

The cAMP receptor protein (CRP) is said to be responsible for positive regulation of the lac operon because ________.

A) CRP levels rise when lactose is present in the environment
B) CRP promotes the production of allolactose
C) CRP prevents binding of the repressor to the operator
D) CRP bound to the CRP-binding site stimulates the transcription of the lac operon

Question 8

When taken up by a cell, which of the following molecules binds to a repressor so that the repressor no longer binds to an operator?

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

Question 9

According to the lac operon model proposed by Jacob and Monod, what is predicted to occur if the operator is removed from the operon?

A) The lac operon would be transcribed continuously.
B) Only lacZ would be transcribed.
C) Only lacY would be transcribed.
D) Genes involved in glucose metabolism would not be transcribed.

Question 10

Which of the following molecules is a protein produced by a regulatory gene?

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

Question 11

If a mutation deactivated a regulatory gene of a repressible operon in an E. coli cell which of the following describes the most likely outcome?

A) continuous transcription of the structural gene controlled by that regulator
B) complete inhibition of transcription of the structural gene controlled by that regulator
C) irreversible binding of the repressor to the operator
D) continuous translation of the mRNA because of alteration of its structure

Question 12

Which of the following predictions about the survival of a lactose intolerant E. coli cell is most likely correct?

A) The cell will survive if the environment has sufficient glucose.
B) The cell will survive if the cell has high levels of lacI expression.
C) The cell will not survive because E. coli require lactose as a nutrient source for life.
D) The cell will not survive because inducible operons must be stimulated for the cell to survive.

Question 13

Under which condition do high levels of transcription of structural genes occur in an inducible operon?

A) It occurs continuously in the cell.
B) It starts when the pathway's substrate is present.
C) It starts when the pathway's product is present.
D) It stops when the pathway's product is present.

Question 14

Which of the following changes in conditions results in an increase in cAMP receptor protein (CRP) mediated initiation of transcription?

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

Question 15

If a researcher moves the operator to the far end of the operon, which of the following processes 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 genes of the lac operon will be transcribed continuously.

Question 16

Which of the following is a molecule that helps to "turn off" the expression of genes in a cell?

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

Question 17

For a repressible operon to be transcribed, which of the following conditions must occur?

A) RNA polymerase must bind to the promoter and a corepressor must be present.
B) RNA polymerase and active repressor must occupy the promoter.
C) RNA polymerase must bind to the promoter, and the repressor must be inactive.
D) RNA polymerase must bind the inducer, and the repressor must be inactive.

Question 18

Prokaryote's ability to regulate patterns of gene expression most likely promotes the organism's survival by ________.

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 an organism to adjust to changes in environmental conditions
D) allowing environmental changes to alter a prokaryote's genome

Question 19

Which of the following molecules binds with a repressor to alter its conformation and therefore affect its function?

A) inducer
B) promoter
C) transcription factor
D) cAMP

Question 20

A mutation in E. coli results in a molecule known as a "super-repressor" because the operon is permanently repressed. Which of the following describes the most likely effect of the mutation on the repressor protein?

A) It cannot bind to the operator.
B) It cannot make a functional repressor.
C) It cannot bind to the inducer.
D) It makes a repressor that binds CAP.

Question 21

Which of the following types of RNA is responsible for helping to reestablish methylation patterns during gamete formation?

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

Question 22

Which of the following functions are characteristic of general transcription factors in eukaryotes?

A) They bind to other proteins or to the TATA box.
B) They inhibit RNA polymerase binding to the promoter and begin transcribing.
C) They are sufficient to allow high levels of transcription.
D) They bind to sequences just after the start site of transcription.

Question 23

Which of the following is the most likely phenotypes of a yeast mutant that contains histones that are resistant to acetylation?

A) The mutant will grow rapidly.
B) The mutant will require galactose for growth.
C) The mutant will show decreased levels of gene expression.
D) The mutant will show increased levels of gene expression.

Question 24

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

A) Environmental signals entering the cell cause the genes to rearrange into related sets.
B) Groups of genes that are expressed together have specific combinations of control elements.
C) Related genes are organized in operons that share a promoter that controls their expression.
D) Release of each gene's individual inducing molecule must be coordinated to coordinate gene expression.

Question 25

Much of the human genome does not code for proteins. Which of the following types of DNA are found in these regions of the genome?

A) DNA that consists only of histone coding sequences
B) DNA that is translated directly without being transcribed
C) DNA that is transcribed into several kinds of small RNAs with biological function
D) DNA that serves as binding sites for reverse transcriptase

Question 26

Which of the following statements correctly describes the primary difference between enhancers and proximal control elements?

A) Enhancers are transcription factors; proximal control elements are DNA sequences.
B) Enhancers improve transcription; proximal control elements inhibit transcription.
C) Enhancers are located considerable distances from the promoter; proximal control elements are close to the promoter.
D) Enhancers are long regions of DNA; proximal control elements are shorter RNA molecules that stand in for DNA.

Question 27

A researcher introduced many copies of a double-stranded RNA into a culture of mammalian cells and used a fluorescent probe to follow it. Later she finds that the introduced strands separate into single-stranded RNAs and she hypothesizes that the molecules is acting as an miRNA. Which of the following pieces of evidence would support her claim?

A) The degradation rate of the single strand is slower than that of other cellular mRNA's.
B) The rate of accumulation of the polypeptide encoded by the target mRNA is reduced.
C) The amount of the RNA she introduced increases due to transcription.
D) After separating the strands she introduced shut down all translation.

Question 28

Which of the following describes how steroid hormones regulate gene expression?

A) They bind to control elements in a regulatory gene and promote synthesis of that operon.
B) They activate translation of certain mRNAs.
C) They promote the degradation of specific mRNAs.
D) They bind to intracellular receptors and alter transcription of specific genes.

Question 29

Which of the following processes is the best way to determine whether alternative splicing of a given gene occurs?

A) Compare the size of the DNA within the given gene and a similar gene in a related organism.
B) Compare the sequences of the given gene and a gene known to undergo alternative splicing.
C) Isolate the primary transcripts made from the given gene and compare the sequences.
D) Isolate mRNA from the given gene and compare the sequences.

Question 30

DNA methylation and histone acetylation are examples of which of the following processes?

A) genetic mutation
B) chromosomal rearrangements
C) epigenetic phenomena
D) translocation

Question 31

If the DNA of a mammalian promoter region experiences increased methylation on cytosine (C) which of the following results is most likely to occur?

A) decreased chromatin condensation
B) activation of histone tails for enzymatic function
C) higher levels of transcription of certain genes
D) inactivation of the gene

Question 32

Which of the following processes destroys RNA molecules if they have a sequence complementary to an introduced double-stranded RNA?

A) RNA interference
B) RNA obstruction
C) RNA blocking
D) RNA disposal

Question 33

Which of the following characteristics of gene expression allows bacteria to quickly change protein synthesis patterns in response to environmental changes?

A) mRNAs that are produced are short-lived and degraded within a few minutes of being synthesized.
B) mRNA have long lifespans, allowing the bacteria to use them many times for translation.
C) mRNA is stored for later use when it is needed later.
D) Operons are activated in the presence of transcription factors.

Question 34

Which of the following statements best describes the characteristics of siRNA?

A) a double-stranded RNA, one of whose strands can complement and inactivate a sequence of mRNA
B) a single-stranded RNA that can fold into cloverleaf patterns due to regions of internal complementary base pairs
C) a double-stranded RNA that is formed by cleavage of hairpin loops in a larger precursor
D) a portion of rRNA that allows it to bind to several ribosomal proteins in forming large or small subunits

Question 35

Which of the following best explains why a neuron and a pancreatic cell isolated from the same individual contain different sets of proteins?

A) The set of genes in each cell type are different, therefore, they express different proteins.
B) Each cell type needs different proteins and, therefore, they break down proteins they don't need.
C) Each cell type contains different regulatory proteins and, therefore, they express different proteins.
D) The genes in each cell type have different promoters and, therefore, they respond to different regulatory proteins.

Question 36

Gene expression is often assayed by measuring the level of mRNA produced from a gene. Which of the following levels of the control of gene expression can by analyzed by this type of assay?

A) replication control
B) transcriptional control
C) alternative splicing
D) translational control

Question 37

A researcher introduced many copies of a double-stranded RNA into a culture of mammalian cells and used a fluorescent probe to follow it. She found that the introduced strands separated; one strand degraded and the other single-stranded RNA remained. The remaining strand is able to do which of the following?

A) attach to histones in the chromatin
B) bind to complementary regions of target mRNAs
C) activate other siRNAs in the cell
D) act as a template for transcription

Question 38

Which of the following methods are used by eukaryotes to control gene expression but are not used by bacteria?

A) organization of genes in operons
B) limiting access to free nucleic acids
C) regulatory proteins binding to promoter sequences and determining polymerase used
D) control of both RNA splicing and chromatin remodeling

Question 39

Which of the following results is most likely to occur if acetylation of histone tails in the chromatin of embryonic cells is increased?

A) increased chromatin condensation
B) decreased chromatin condensation
C) decreased binding of transcription factors
D) inactivation of the selected genes

Question 40

Assays analyzing transcriptional control of gene expression focus on which of the following characteristics?

A) number of copies of the gene in the organism
B) size of the gene's open reading frame
C) relative level of the protein produced
D) amount of the mRNA generated

Question 41

Forms of the Ras protein found in tumors usually cause which of the following events to occur?

A) DNA replication to stop
B) decreased cell-to-cell adhesion
C) cell division to cease
D) excessive cell division

Question 42

If a mutation alters a maternal effect gene in a female Drosophila zygote, which of the following is most likely to occur?

A) She will not develop past the early embryonic stage.
B) All of her offspring will show the mutant phenotype, regardless of their genotype.
C) Only her male offspring will show the mutant phenotype.
D) Only her female offspring will show the mutant phenotype.

Question 43

The product of the bicoid gene in Drosophila is responsible for determining which of the following embryonic features or structures during development?

A) orientation of the dorsal-ventral axis
B) orientation of the left-right axis
C) segmentation of developing limbs
D) orientation of the anterior-posterior axis

Question 44

Which of the following statements correctly describes a characteristic of tumor-suppressor genes?

A) They are frequently overexpressed in cancerous cells.
B) They are cancer-causing genes introduced into cells by viruses.
C) They encode proteins that help prevent uncontrolled cell growth.
D) They often encode proteins that stimulate the cell cycle.

Question 45

Muscle cells differ from nerve cells mainly because they ________.

A) express different genes
B) contain different genes
C) use different genetic codes
D) have unique ribosomes

Question 46

Which of the following explains why introducing the MyoD protein into a fat cell causes that cell to become a muscle cell but adding it to a neuron will have no effect?

A) Fat cells are undifferentiated, the MyoD protein causes them to differentiate.
B) Neurons are a differentiation step after muscle cells, they cannot go "backwards."
C) Muscle-specific gene expression requires a protein that neurons do not make.
D) MyoD is causes positive feedback of MyoD expression in fats cells but not neurons.

Question 47

Which of the following describes the role typical proto-oncogenes have when they are expressed in cells that are not cancerous?

A) They suppress tumor growth.
B) They inhibit differentiation.
C) They stimulate normal cell growth and division.
D) They enhance signaling from growth factor receptors.

Question 48

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 49

Which of the following conclusions is consistent with the fact that plants can be cloned from somatic cells?

A) Differentiated cells retain all the genes of the zygote.
B) Differentiation results in the loss of non-expressed genes.
C) The differentiated state is normally very unstable.
D) Differentiation does not occur in plants.

Question 50

Cell differentiation always involves ________.

A) transcription of the myoD gene
B) the movement of cells
C) the production of tissue-specific proteins
D) the selective loss of certain genes from the genome

Question 51

Cytoplasmic determinants are best described as having which of the following characteristics?

A) They are maternal substances in the egg that influence the course of early development.
B) They are single-stranded RNA molecules capable of binding complementary sequences and altering translation.
C) They are centromeric regions of DNA loosened for chromosomal replication by transcription factors.
D) They are tissue-specific transcription factors expressed in the early embryo.

Question 52

Which of the following characterizes BRCA1 and BRCA2 as tumor-suppressor genes?

A) Their normal products participate in repair of DNA damage.
B) The mutant forms of either one of these prevent breast cancer.
C) The normal genes code for estrogen receptors.
D) They block penetration of breast cells by chemical carcinogens.

Question 53

In wildtype Drosophila embryos, the bicoid mRNA is localized to the anterior end of the embryo. If bicoid mRNA was injected into the embryo's posterior end as well, which of the following developmental events would occur?

A) The embryo would grow extra wings and legs.
B) The embryo would have altered segmentation.
C) The embryo would show anterior structures at both ends of the embryo.
D) The embryo would develop normally.

Question 54

Which of the following types of mutation would convert a proto-oncogene into an oncogene?

A) a mutation that blocks transcription of the proto-oncogene
B) a mutation that greatly reduces the stability of a proto-oncogene mRNA
C) a mutation that greatly increases the amount of the proto-oncogene protein
D) a deletion of most of the proto-oncogene coding sequence

Question 55

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 56

In colorectal cancer, several genes must be mutated for a cell to develop into a cancer cell. Which of the following kinds of genes would you expect to be mutated?

A) genes coding enzymes that act in the colon
B) genes involved in control of the cell cycle
C) genes that are especially susceptible to mutation
D) genes regulating cell division in colon bacteria

Question 57

Mutations in which of the following genes result in transformations in the identity of entire body parts?

A) segmentation genes
B) egg-polarity genes
C) homeotic genes
D) inducers

Question 58

A cell is considered to be differentiated if it has which of the following characteristics?

A) The cell replicates by the process of mitosis.
B) The cell loses connections to the surrounding cells.
C) The cell produces proteins specific to a particular cell type.
D) The cell appears to be different from the surrounding cells.

Question 59

Which of the following describes the normal function of the p53 gene product?

A) It inhibits the cell cycle.
B) It slows down the rate of DNA replication by interfering with the binding of DNA polymerase.
C) It causes cells to reduce expression of genes involved in DNA repair.
D) It allows cells to pass on mutations due to DNA damage.

Question 60

A genetic test to detect predisposition to cancer would likely examine the APC gene for involvement in which type(s) of cancer?

A) colorectal only
B) lung and breast
C) lung only
D) lung and prostate

Question 61

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 62

Absence of bicoid mRNA from a Drosophila egg leads to the absence of anterior larval body parts and mirror-image duplication of posterior parts. This is evidence that the product of the bicoid gene ________.

A) normally leads to formation of head structures
B) normally leads to formation of tail structures
C) is transcribed in the early embryo
D) is a protein present in all head structures

Question 63

Which of the following statements about the 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) Each gene lies immediately adjacent to an enhancer.

Question 64

Within a cell, the amount of protein made using a given mRNA molecule in that cell depends partly on ________.

A) the degree of DNA methylation
B) the rate at which the mRNA is degraded
C) the number of introns present in the mRNA
D) the types of ribosomes present in the cytoplasm

Question 65

Proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cells?

A) Proto-oncogenes first arose from viral infections.
B) Proto-oncogenes are mutant versions of normal genes.
C) Proto-oncogenes are genetic "junk."
D) Proto-oncogenes normally help regulate cell division.

Question 66

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) gene amplification contributing to cancer