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