ch 20
enhancers can be found
5' or '3 or end of gene or even within a gene
Which of the following regulatory elements is not composed of DNA sequences?
Activators
A eukaryotic gene is observed to make multiple forms of a protein. How can one eukaryotic gene produce multiple products in the same cell?
Alternative splicing sites can lead to the production of two different mature mRNAs from the same gene, resulting in slightly different proteins.
pattern formation
Cells receive molecular signals that communicate their position in relation to other cells
Hox genes
Class of homeotic genes. Changes in these genes can have a profound impact on morphology.
cis-acting factors
DNA sequences in the vicinity of a gene required for gene expression
pattern formation
Differential gene expression affects the developmental process in animals.
An enhancer may increase the frequency of transcription initiation for its associated gene when no promoter is present.
False. Enhancer cannot increase the rate of transcription of a gene unless the gene has a core promoter.
An enhancer may increase the frequency of transcription initiation for its associated gene when it causes alternative splicing of the DNA.
False. Enhancers have not been shown to play a role in DNA splicing.
pattern formation
Homeotic genes code for transcription factors that control the development of segment-specific body parts.
The operon model of the regulation of gene expression in bacteria was proposed by _____.
Jacob and monod
Which of the following terms describes the DNA-protein complexes that look like beads on a string?
Nucleosome
pattern formation
Positional information controls pattern formation.
Which of the following events in transcription initiation likely occurs last?
RNA polymerase binds to the promoter of the gene.
What is the function of a spliceosome?
RNA processing
Spliceosomes are involved in
RNA processing.
A student is interested in using genetic mutation as a mechanism to disrupt steroid hormone receptor-mediated transcription in a eukaryotic cell culture. Which of the following would NOT be a viable strategy to accomplish this task?
Steroid hormone receptors act as transcription factors by binding to DNA control sequences known as hormone response elements. Steroid hormone receptors contain three functional domains: one that binds to the response element in the DNA, one that binds to the steroid hormone, and one that activates transcription. Mutating any one or all of these domains would theoretically disrupt steroid hormone receptor-mediated transcription in a eukaryotic cell culture.
Which of these statements about enhancers is correct?
They are functional in locations similar to those where silencers are found.
An enhancer may increase the frequency of transcription initiation for its associated gene when it is located 1000 nucleotides upstream of the gene's core promoter.
True. Enhancers have been shown to increase rates of transcription initiation even when located up to tens of thousands of base pairs from the promoter that they affect.
An enhancer may increase the frequency of transcription initiation for its associated gene when it is in the gene's coding region.
True. In a few cases, enhancers located within genes have been identified and observed to increase transcription levels.
trans-acting factors
a regulatory protein that binds to a regulatory element in the DNA and exerts a trans effect
genes of the operon code for
a related set of proteins
In eukaryotes, post-transcriptional control of gene regulation may involve
alternative mRNA splicing, control of nuclear export of mRNAs to the cytoplasm, and differential mRNA degradation.
A researcher is studying a new bacterium discovered in the water pipes of an old home. The researcher is particularly interested in a small operon that controls the formation of a biofilm under low nutrient conditions. The operon consists of three genes, A, B, and C, in that order from the promoter. The researcher performs site-directed mutagenesis on gene B in the operon, and then introduces a fresh copy of gene B on a plasmid under the control of an inducible promoter. After induction of the plasmid, the expression of all genes in the operon is restored. What conclusion can be drawn from this experiment?
b gene is trans-acting factor
Hox genes determine an animal's
body plan
Bacteria that use the lac operon are grown in a laboratory under conditions of high lactose and no glucose. A researcher then adds progressively more and more glucose to the bacteria. Which of the following describes the temporal changes the bacteria experience in this experiment?
cAMP levels will fall and expression of the lac operon will decrease as a function of time in the experiment.
Enzymes that add ubiquitin to proteins have been found in the nucleus of eukaryotic cells. These enzymes would be most likely to regulate gene expression by __________.
causing degradation of transcription factors and changing which genes are expressed
pattern formation is
development of a multicellular organism's spatial organization, including the arrangment of tissues and organs
greek key motif is in protein folding but not in
dna binding
in prokaryotes the repressor binds to
dna in or near the promoter
Which of the following regulatory DNA sequences might be located thousands of nucleotides away from the transcription start site of a gene?
enhancer
homeotic genes are only found in
eukaryotes
True or false? One possible way to alter chromatin structure such that genes could be transcribed would be to make histone proteins more positively charged
false
True or false? Regulatory and basal transcription factors regulate transcription by binding to the promoter.
false
A student is attempting to engineer a novel DNA-binding protein that can be used to silence gene expression in eukaryotic expression plasmids. Which of the following protein motifs would NOT be a potential design to consider for this bio-engineering project?
greek key motif
A researcher is attempting to activate cAMP-stimulated genes in a cell line that has a defective adenylyl cyclase enzyme. The researcher adds a membrane-permeant, nonhydrolyzable analog of cAMP to the cells. Which of the following would be a reasonable output to determine if this membrane-permeant, nonhydrolyzable analog of cAMP will activate cAMP-stimulated genes?
histone deacetylation in cAMP-responsive genes
Genes associated with embryonic development are known as
homeotic genes
Effector molecules can
induce conformational changes.
You are examining a bacterial enzyme associated with glycolysis. You would expect expression of the enzyme to be
induced by glucose
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?
insulator
genes of an operon
is arranged sequentially after the promoter
trp operon
is regulated through negative control only
The catabolism of lactose involves all of the following EXCEPT __________.
lac inducer protein
lac operon is regulated through
negative and positive control
In the presence of a regulatory protein the lac operon is _____.
not transcribed
when tryptophan is present in the trp operon, operon genes are
not transcribed
enhancers can function thousnads of
nucleotides away from promoter and transcription start site
promoter is a stretch
of dna where rna polymerase binds
Regulatory proteins bind to _____.
operator
promoter includes an
operator
Regulatory proteins bind to _____.
operator, to control expression of the operon
regulatory gene is not part of an
operon
RNA polymerase is recruited only when
other transcription factors, including TBP, are assembled at the promoter.
basal transcription factors bind to
promoter
an operon is made up of
promoter and genes of the operon
activator are
proteins involved in transcription initiation
regulatory gene plays a role in
regulating the expression of an operon
The nuclear membrane's role in the regulation of gene expression involves _____.
regulating the transport of mRNA to the cytoplasm
Which of these is NOT a component of the lac operon?
regulatory gene only
transcription is inhibited when a
regulatory protein binds to the lac operon operator
You are examining an enzyme associated with cysteine biosynthesis. You would expect expression of the enzyme to be
repressed by cysteine.
One mechanism that may lead to novel disease treatment involves ________, which hinders the translation of specific mRNAs.
siRNA
an inducer is a
specific small molecule that binds to a bacteral regulatory protein and changes its shape so that it cannot bind to an operator, switching an operon on
hopanoids
sterol-like molecules found in bacteria
an operon is a
stretch of DNA consisting of an operon, promoter, and genes for related set of proteins, usually making up an entire metabolic pathway
Lactose inactivates the repressor so...
that the lactose-utilization genes can be transcribed
regulatory proteins bind to
the operator
RNA polymerase
transcribed the genes of the lac operon
Hox genes code for
transcription factors
Which of these processes is involved in gene regulation in both eukaryotes and prokaryotes?
transcriptional control
Protein phosphorylation and dephosphorylation can affect __________.
transcriptional, translational, and posttranslational control
homologous genes
two genes derived from the same ancestral gene
If the gene encoding the lac repressor is mutated so that the repressor can no longer bind the operator, will a high level of transcription of that operon occur?
yes, because RNA polymerase will be able to bind the promoter and transcribe the operon
Hox genes are known to influence the identity of body parts in mammals, similar to their role in flies. Mario Capecchi's laboratory has made many knockout mouse strains in which individual Hox genes are knocked out. The phenotype of many of these knockouts is extremely mild, especially when compared with the corresponding mutants in flies, which often die. how do you explain the difference?
Mammals have four sets of Hox genes, whereas flies only have a single set. Because in some cases more than one of the mammalian Hox clusters encodes a similar protein, mutations in some of the mammalian Hox genes have mild phenotypes.
The genes responsible for catabolism of the amino acid methionine in bacteria are not transcribed or translated in the absence of methionine. When methionine is added to the bacteria, genes for methionine are turned on. Which of the following is the likely scenario for initiation of transcription of methionine transcription genes?
Methionine is an inducer that binds to a genetic repressor protein
An enhancer may increase the frequency of transcription initiation for its associated gene when it causes looping out of the intervening DNA
True. Enhancers appear to act by forming a loop of DNA as the activators bound to the enhancer bind to coactivators that are subunits of TFIID, which in turn binds to the promoter.
promoter is a
a specific sequence of DNA nucleotides that binds to rna polymerase, positioning it to start transciribing rna at the appropriate places
Which of the following processes is/are associated with the modification of histone proteins in vivo?
acetylation and methylation
Effector molecules
are associated with the induction of enzyme synthesis.
Effector molecules
are associated with the repression of enzyme synthesis.
Effector molecules
are often small organic molecules.
heterologous genes
cloned genes in the new host cell
regulatory gene
codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes
positive control
glucose is present, regulatory protein (CAP) binds to promoter of the lac operon, increasing rate of transcription if lactose is present
the regulatory gene is not
part of the operon
proteins are often activated by
phosphorylation
The situation in which an active regulatory protein "turns on" gene expression is an example of
positive control
Protein phosphorylation, protein folding, and proteolytic cleavage are all examples of
post- translational control of gene expression and activity
The ubiquitination of a protein will often result in its being targeted for degradation by the proteasome. This is an example of what type of eukaryotic gene expression regulation?
posttranslation
regulatory transcription factors bind to
promoter-proximal elements and enhancers
enzymes complexes that break down proteins are
proteasomes
Protein-phosphorylating enzymes' role in the regulation of gene expression involves _____.
protein activation
repressor is a
protein that inhibits gene transription,
sigma factors
proteins in prokaryotic cells that bind to RNA polymerase and direct it to specific classes of promoters
a regulatory protein of the lac operon is a
repressor
negative control when lactose is absent
repressor protein is active transcription is turned off
negative control when lactose is present
the repressor protein is inactivates, transcription is turned off
DNA-binding domains/motifs in proteins are
the zinc finger motif, the leucine zipper motif, and the helix-loop-helix motif
Which of these statements is NOT true of homeotic genes?
they are found in all organisms