Deck 16: Regulation of Gene Expression

Question 1

If the lacI repressor gene were permanently silenced by a DNA mutation, what would be the impact on the expression of the lac operon?

A) The lac operon would only be expressed if glucose were absent.
B) The lac operon would always be expressed.
C) There would be no impact on lac operon expression.
D) The lac operon would only be expressed when lactose was present.
E) The lac operon would never be expressed.

Answer 1

B

Question 2

Where is the trp repressor gene located?

A) Just upstream of the trp operon
B) On a region of the chromosome at some distance from the trp operon
C) Adjacent to the lac repressor gene
D) Just downstream of the trp operon
E) Directly adjacent to the promoter region of the trp operon

Answer 2

B

Question 3

The trp operon is ____ unless tryptophan is ____.

A) turned on; available in the environment
B) turned on; bound to the operator
C) turned off; bound to the repressor
D) turned off; bound to the promoter
E) turned on; synthesized by the trp repressor gene

Answer 3

A

Question 4

Genes under positive control are ____.

A) off until they are turned on
B) always expressed
C) expressed unless a repressor protein is present
D) controlled by several promoters to increase transcription
E) regulated by feedback inhibition

Question 5

Regulatory proteins bind to the ____ of a gene operon.

A) transcription unit only
B) promoter only
C) operator only
D) transcription unit and promoter
E) operator and promoter

Question 6

What is the relationship between operons and transcription units?

A) They are synonymous terms.
B) An operon consists of a transcription unit plus associated regulatory DNA sequences.
C) A transcription unit consists of an operon plus associated regulatory DNA sequences.
D) An operon is composed of multiple transcription units.
E) A transcription unit is composed of multiple operons.

Question 7

The genes in an operon are ____.

A) each transcribed into individual mRNAs
B) transcribed into a single mRNA transcript
C) controlled by separate promoters
D) transcribed as a single mRNA in prokaryotes, but as individual mRNAs in eukaryotes
E) located at different chromosomal loci

Question 8

In prokaryotes, high levels of cAMP ____.

A) are present when glucose levels are high
B) are present when glucose levels are low
C) negatively regulate the lac operon
D) promote CAP production
E) lead to CAP degradation

Question 9

In prokaryotes, the genes for metabolic pathways are ____.

A) always expressed for early steps in the pathway, but generally not expressed for later steps in the pathway
B) always expressed so the bacteria can respond to rapidly  changing conditions
C) turned on and off as conditions change
D) always independently regulated
E) generally expressed at low levels, but expressed at high levels when conditions warrant

Question 10

The E. coli lac operon encodes three genes. These genes ____.

A) cleave lactose into glucose and galactose, produce transacetylase, and actively transport lactose into the cell
B) encode an enzyme that cleaves glucose, a transport protein for active transport, and a transacetylase enzyme for solubilizing lactose in the cytosol
C) encode an enzyme that cleaves lactose, a transport protein for active transport of lactose, and a transacetylase enzyme whose function is unknown
D) catalyze the synthesis of lactose from glucose and galactose, produce transacetylase, and actively export lactose from the cell
E) directly interact with the Lac repressor and initiate their own transcription

Question 11

How is lac operon transcription regulated by the presence or absence of lactose?

A) When lactose is available, the repressor will bind to allolactose instead of blocking RNA polymerase by binding to the operator.
B) When lactose is not available, the repressor will bind to the promoter and block RNA polymerase from binding to the promoter.
C) When lactose is not available, the repressor will bind to allolactose.
D) When lactose is available, allolactose is produced and binds to the operator, blocking RNA polymerase.
E) In the absence of lactose, transcription occurs at a low level, resulting in the production of allolactose, which, in turn, stimulates the cell to take up lactose.

Question 12

Genes expressed in almost all cell types are called ____ genes.

A) housekeeping
B) regulated
C) activator
D) homeotic
E) structural

Question 13

When lactose is present in the medium, RNA polymerase will bind to the ____ of the E. coli lac operon.

A) lacI gene
B) operator
C) promoter
D) transcription initiation site
E) first codon of the lacZ gene

Question 14

The trp operon is an example of a(n) ____ operon where tryptophan acts as a(n) ____.

A) inducible; inducer
B) inducible; activator
C) repressible; corepressor
D) repressible; repressor
E) repressible; inducer

Question 15

Transcription of the lac operon is most efficient when ____.

A) cAMP levels are low
B) the CAP site of the promoter is not bound to cAMP
C) glucose is present and lactose is absent
D) lactose is present and glucose is absent
E) lactose and glucose are present

Question 16

In the lac operon, CAP binding to the CAP site of the promoter ____.

A) occurs when glucose is present
B) inhibits RNA polymerase from binding to the promoter
C) occurs when cAMP is absent
D) helps the repressor protein bind to the operator
E) enables RNA polymerase to transcribe the operon's genes

Question 17

What is the relationship between operators, transcription units, and operons?

A) Operators contain transcription units and operons.
B) Operons contain transcription units and operators.
C) Operators contain multiple transcription units associated with a single operon.
D) Operons contain multiple operators associated with a single transcription unit.
E) Operons contain multiple transcription units associated with a single operator.

Question 18

If an operon is regulated by ____ control, genes are ____ by a regulatory protein called a ____.

A) positive; on unless they are switched off; repressor
B) negative; off unless they are switched on; repressor
C) negative; on unless they are switched off; repressor
D) positive; off unless they are switched on; repressor
E) positive; on unless they are switched off; activator

Question 19

The primary difference between individual nucleated cells in a developing zygote is the ____.

A) genetic code of each cell
B) differential expression of housekeeping genes
C) differential expression of regulated genes
D) number of chromosomes present in the nucleus
E) presence or absence of gene regulatory sequences

Question 20

Gene regulation in both prokaryotes and eukaryotes ____.

A) involves significant chromatin remodeling
B) requires transcription and translation to occur in separate cellular compartments
C) produces differentiated cells
D) involves transcriptional control
E) involves alternative splicing

Question 21

Variations in pre-mRNA processing, such as in ____, can determine which ____ are made in cells.

A) alternative splicing; proteins
B) exon shuffling; proteins
C) alternative splicing; transcripts
D) histone modifications; transcripts
E) genomic imprinting; transcripts

Question 22

Changes in pre-mRNA processing and the rate at which mRNAs are degraded are a part of ____.

A) histone modifications
B) chromatin remodeling
C) transcriptional regulation
D) posttranscriptional regulation
E) genomic imprinting

Question 23

Steroid hormones can trigger gene expression in a select number of cells because ____.

A) only target cells allow the steroid hormone to cross the plasma membrane
B) nontarget cells have a steroid hormone response element encoded in their DNA
C) only target cells have the correct receptor in their cytosol to bind to the hormone
D) nontarget cells lack the genes found in target cells
E) only target cells have the genes that steroid hormones activate

Question 24

Which statement about eukaryotic gene organization and regulation is correct?

A) There is only one promoter for each gene.
B) There is only one transcription start site (TSS) for each gene.
C) A gene may have more than one promoter and more than one transcription start site (TSS).
D) Transcription start sites (TSSs) are highly evolutionarily conserved.
E) Data shows there are more genes than promoters in the human genome.

Question 25

Other than the proteins that they encode, what is a major difference between cell-specific and housekeeping genes?

A) Cell-specific genes are expressed only in a single cell type; housekeeping genes are expressed in all cell types.
B) Cell-specific genes have promoter proximal elements and enhancers; housekeeping genes have only promoter proximal elements.
C) Cell-specific genes have promoter proximal elements that use cell-specific activators; housekeeping genes use "universal" activators found in all cells.
D) Cell-specific genes are only found in certain cell types; housekeeping genes are found in all cell types.
E) Cell-specific genes have promoter proximal elements that use "universal" activators found in all cells; housekeeping genes have promoter proximal elements that respond only to cell-specific activators.

Question 26

Which level of regulation directly determines the rate at which proteins are made?

A) transcriptional regulation
B) posttranscriptional regulation
C) translational regulation
D) posttranslational regulation
E) chromatin remodeling regulation

Question 27

Long noncoding RNAs ____.

A) are transcribed by RNA polymerase I rather than by RNA polymerase II
B) do not have their introns removed
C) are missing a 5' cap and 3' poly(A) tail
D) may regulate the expression of protein-coding genes
E) encode large proteins

Question 28

Removing a nucleosome from DNA to expose a promoter is an example of ____.

A) induction
B) dedifferentiation
C) post-transcriptional regulation
D) gene silencing
E) chromatin remodeling

Question 29

In eukaryotes, ____ regulation is the first level at which gene expression is controlled.

A) transcriptional
B) translational
C) posttranscriptional
D) posttranslational
E) replicative

Question 30

An enhancer is a sequence that increases transcription of a gene ____.

A) when its orientation is the same as that of the gene it controls
B) when it is located just downstream of the promoter
C) when it is located just upstream of the promoter
D) when it is distant from the gene it controls
E) independently of its position, orientation, and distance from a promoter

Question 31

How does RNA polymerase II bind to the DNA?

A) It binds directly to the eukaryotic promoter sequence.
B) It binds directly to the TATA box.
C) It binds to transcription factors in the nucleus, and the complex then binds to the promoter.
D) Transcription factors first bind to the promoter, then recruit RNA polymerase II to that site.
E) Some transcription factors bind to the promoter, while others bind to RNA polymerase II, then the two groups of proteins bind to each other.

Question 32

In eukaryotic cells, ____.

A) gene expression is regulated mostly at the level of transcription
B) all mRNAs tend to remain stable for about the same length of time
C) mRNA activity is altered through modifications, such as phosphorylation
D) promoters are typically "on" in the absence of regulatory proteins
E) genes involved in similar processes are clustered together in operons

Question 33

Acetylation adds a ____ group ____.

A) CH₃CO-; to the cytosine nucleotides of DNA
B) CH₃CH₂-; to the DNA of a promoter sequence
C) CH₃CO-; to the histone protecting the transcription unit of a gene
D) CH₃CO-; to the histone protecting the promoter region of a gene
E) CH₃CH₂-; to the RNA polymerase that will initiate transcription at the promoter region

Question 34

Gene silencing ____.

A) cannot be inherited
B) occurs when DNA is methylated
C) occurs due to histone acetylation
D) is an example of posttranscriptional regulation
E) occurs only on the X chromosome

Question 35

A bridge is formed between the activators at the enhancer and the proteins at the promoter and promoter proximal region by ____.

A) hormones
B) RNA polymerase II
C) repressors
D) inducers
E) coactivators

Question 36

When a DNA promoter sequence is methylated, ____.

A) it is permanently silenced because the methyl group can never be removed
B) it is temporarily silenced because the methyl group can be removed
C) it is perpetually transcribed because the methyl group can never be removed
D) it is temporarily transcribed because the methyl group can be removed
E) the impact on expression depends on the gene being controlled by the promoter

Question 37

Eukaryotic cells regulate the expression of multiple genes by having ____.

A) individual activators for individual genes
B) a few activators that can interact with small subsets of genes
C) activators that serve as catalysts for further activator protein synthesis
D) a few activators that work in different combinations to activate different genes
E) a single activator that undergoes modifications to enable interaction with different promoters

Question 38

When histones are rearranged to control gene access, it is called ____.

A) transcription
B) chromatin remodeling
C) DNA condensation
D) remodeling complex formation
E) acetylation

Question 39

Some transcriptional repressors work by ____.

A) binding to the same sequence where activators normally bind
B) binding to and disabling the activator
C) recruiting histone acetylation enzymes and thus interfering with chromatin remodeling
D) binding to RNA polymerase II and preventing it from binding to the transcription factor complex
E) methylating DNA

Question 40

Methylation regulates transcription by ____.

A) adding a methyl group to cytosine bases of DNA
B) adding a methyl group to cysteine residues on RNA polymerase II
C) adding a methyl group to cysteine bases of DNA
D) adding a methyl group to cytosine residues on RNA polymerase II
E) interfering with the chromatin remodeling process

Question 41

Hox genes, one class of ____ genes, contain a conserved ____ region and encode transcription factors.  These encoded transcription factors contain a _____ that corresponds to the conserved region in the Hox genes and binds to the regulatory sequences of the target genes whose transcription they regulate.

A) maternal-effect; homeodomain; homeobox
B) segmentation; homeobox; homeodomain
C) segmentation; homeodomain; homeobox
D) homeobox; homeobox; homeodomain
E) homeobox; homeodomain; homeobox

Question 42

A cell that is totipotent ____.

A) has the potential to become any cell type of the adult
B) induces nearby cells to follow a certain developmental pathway
C) will never differentiate
D) will not undergo determination
E) has unregulated gene expression

Question 43

Which process sets the developmental fate of an embryonic cell?

A) fertilization
B) meiosis
C) induction
D) differentiation
E) determination

Question 44

Which statement accurately describes the relationship between RNAi, small interfering RNA (siRNA), and miRNA?

A) They all describe different methods of post-translational gene regulation.
B) miRNAs are classified into two types: RNAi molecules and siRNAs.
C) RNAi occurs in two ways: by miRNAs or by siRNAs.
D) RNAi is accomplished by siRNA and miRNA, but only siRNAs are cleaved by Dicer proteins.
E) miRNAs are transcribed from viruses, while siRNAs are transcribed from nuclear DNA; both are types of RNAi.

Question 45

The anterior-posterior orientation of Drosophila embryos is initially controlled and determined by ____.

A) maternal-effect genes
B) gap genes
C) pair rule genes
D) segment polarity genes
E) homeotic genes

Question 46

In RNAi, imperfect pairing of miRNA to target mRNA results in ____ or ____, while perfect pairing of miRNA to target mRNA causes ____.

A) blocking transcription of the target mRNA; a shorter half-life for the mRNA; mRNA degradation
B) blocking translation of the target mRNA; a shorter half-life for the mRNA; mRNA degradation
C) recruitment of siRNA; a shorter half-life for the mRNA; blocking translation of the target mRNA
D) mRNA degradation; a longer half-life for the mRNA; recruitment of siRNA
E) blocking target mRNA transcription; blocking translation of the target mRNA; a longer half-life for the mRNA

Question 47

Experiments with mouse cells indicate that long noncoding RNAs ____.

A) block cardiac cell development
B) play a critical role in cardiac cell differentiation
C) are not expressed in embryonic stem cells
D) are only expressed after cardiac cells have differentiated
E) are transcription factors that promote cardiac cell differentiation

Question 48

The expression of any gene can be _______ using ____.

A) knocked out completely; miRNA
B) knocked out completely; siRNA
C) knocked out completely; RNAi
D) knocked down to low levels; RNAi
E) knocked down to low levels; siRNA, but not miRNA

Question 49

A tumor comprised of cells that invade and disrupt surrounding tissues is called a(n) ____ tumor.

A) benign
B) malignant
C) oncogenic
D) unsuppressed
E) familial

Question 50

Why is ubiquitin nicknamed the "doom tag"?

A) When ubiquitin binds to a target protein, the ubiquitin enzyme degrades the protein.
B) When ubiquitin binds to a target protein, the complex is sent to the proteasome and degraded.
C) If a cell is deficient in ubiquitin, the cell will die.
D) High levels of ubiquitin in a cell cause the cell to destroy vital proteins, leading to premature cell death.
E) Ubiquitin binds to ribosomes and prevents them from translating proteins necessary for cell survival.

Question 51

Micro RNAs (miRNAs) are important in ____.

A) alternative splicing
B) transcriptional activation
C) chromatin remodeling
D) genomic imprinting
E) RNA interference (RNAi)

Question 52

Increases in poly(A) tail length result in increased ____.

A) transcription
B) translation
C) protein stability
D) mRNA degradation
E) alternative splicing

Question 53

When cells differentiate, they ____.

A) lose DNA
B) remain totipotent
C) express a specific subset of genes
D) stop growing
E) gain DNA

Question 54

Transcription factors that control genes for developmental events are encoded by ____ genes.

A) transcriptomes
B) domestic
C) master regulatory
D) elevator
E) secretory

Question 55

Posttranslational modification includes ____.

A) cleavage of poly-A tails from mRNA
B) the binding of miRNAs to mRNA
C) the chemical modification, processing, and degradation of proteins
D) chromatin remodeling
E) splicing of mRNAs

Question 56

Sporadic cancers ____.

A) may develop when proto-oncogenes mutate to form tumor suppressor genes
B) may develop when tumor suppressor genes are over-expressed
C) are caused by benign tumors
D) are cancers that are not inherited
E) are less frequent than familial cancers

Question 57

Pepsin, a digestive enzyme that degrades proteins in the stomach, is synthesized as pepsinogen and converted to active pepsin in the stomach by the removal of several amino acids. The activation of pepsin is an example of ____.

A) transcriptional regulation
B) translational regulation
C) posttranscriptional regulation
D) posttranslational regulation
E) RNAi

Question 58

A small molecule of RNA is transcribed in the nucleus. It is folded, cleaved by the Dicer enzyme, forms a complex with proteins, which then binds to a target molecule of mRNA. This molecule of RNA must be ____.

A) miRNA
B) siRNA
C) an mRNA that was not properly capped
D) an mRNA that never received its poly-A tail
E) a transcript for a repressor protein

Question 59

One function of the 3' UTR (untranslated region) of mRNA is to ____.

A) control the half-life of mRNA
B) bind RNA polymerase to initiate transcription
C) help activators bind to the enhancer region
D) base pair with the translated region of the transcript to mark it for degradation
E) bind ribosomes to initiate translation

Question 60

Cytoplasmic determinants are ____.

A) key mRNAs and proteins stored in the sperm cytoplasm that direct the early stages of development
B) key mRNAs and proteins stored in the egg cytoplasm that direct the early stages of development
C) evenly distributed throughout the egg cell
D) distributed symmetrically to daughter cells
E) proteins from the egg and sperm cytoplasm that interact to form novel protein complexes in the zygote

Question 61

Many proto-oncogenes encode ____.

A) growth-inhibiting factors
B) intracellular receptors
C) tumor suppressor proteins
D) receptors for growth-inhibiting factors
E) growth factors

Question 62

RNAi could be used as an anti-viral treatment by ____ and thus preventing viral infection and spread.

A) degrading the viral genome or mRNAs and stopping key viral protein production
B) increasing immune system response to the virus
C) binding to receptors on host cells used for viral entry
D) promoting expression of viral DNA-degrading enzymes
E) stimulating host cells to produce anti-viral compounds

Question 65

In a process called ____, cells lose their normal regulatory controls and revert partially or completely to an embryonic developmental state.

A) metastasis
B) embryogenesis
C) induction
D) determination
E) dedifferentiation

Question 66

Explain the concept of combinatorial gene regulation in eukaryotes.

Question 67

Compare the functions of maternal-effect genes, segmentation genes, and homeotic genes in Drosophila .

Question 68

Many breast cancers are associated with mutations in the BRCA1 gene. Explain the difference between sporadic and familial breast cancer caused by this gene at a molecular level.

Question 69

The role of a tumor suppressor protein in a cell is to ____.

A) promote cell division of healthy cells
B) inhibit cell growth and division
C) promote cell division of abnormal cells
D) trigger DNA replication in preparation for cell division
E) serve as a cell receptor for growth factors

Question 70

Oncogenes are ____ to ____.

A) dominant; proto-oncogenes
B) recessive; proto-oncogenes
C) incompletely dominant; proto-oncogenes
D) dominant; tumor suppressor genes
E) recessive; tumor suppressor genes

Question 71

An unmutated version of an oncogene in a normal cell is called a ____.

A) growth-inhibiting factor gene
B) driver gene
C) proto-oncogene
D) pre-oncogene
E) tumor suppressor gene

Question 72

Explain the difference between benign and malignant tumors.

Question 73

The default state for the lac operon is "off," while the default state for the trp operon is "on." Explain this difference in regulation and the mechanism of control via the repressor proteins.

Question 74

p53 is a ____.

A) transcription factor that turns on the expression of cell-division-inhibiting proteins
B) protein encoded by an oncogene
C) protein that promotes entry into the cell cycle when DNA is undamaged
D) hormone used to treat cancer
E) growth-promoting factor

Question 75

Which genes encode proteins that regulate the cell cycle in normal cells?

A) tumor suppressor genes
B) proto-oncogenes
C) oncogenes
D) tumor suppressor genes and proto-oncogenes
E) tumor suppressor genes, proto-oncogenes, and oncogenes

Question 76

When a(n) ____ by mutation, it confers a selective growth advantage to the cell.

A) tumor suppressor gene is activated
B) oncogene is inactivated
C) proto-oncogene is inactivated
D) tumor suppressor gene is inactivated
E) apoptosis gene is activated

Question 77

A key difference between eukaryotic and prokaryotic genomes is ____.

A) the lack of gene expression controls in prokaryotes
B) the physical arrangement of genes on the chromosome(s)
C) simultaneous transcription and translation in eukaryotes vs. sequential transcription and translation in prokaryotes
D) the physical separation of transcription and translation in prokaryotes compared to the lack of separation of these processes in eukaryotes
E) the regulation of the cell cycle by prokaryotes, which is not observed in eukaryotes.

Question 78

Compare DNA methylation to histone acetylation.

Question 79

Which statement correctly describes BRCA ?

A) Mutations to BRCA2 appear to be more lethal than mutations to BRCA1 .
B) It is an oncogene associated with breast cancer.
C) It is a tumor suppressor gene associated with breast cancer.
D) BRCA mutations are not inherited.
E) BRCA is a proto-oncogene involved in breast tissue development.

Question 80

A driver gene ____.

A) contains a driver mutation that does not affect gene expression
B) does not have any effect on cancer progression
C) contains a driver mutation that causes apoptosis in normal cells
D) contains a driver mutation or is expressed abnormally and confers a growth advantage on the cell
E) is the unmutated form of a proto-oncogene