18 Regulation of Gene Expression

Which of the following is/are involved in controlling eukaryotic gene expression? a. transcriptional regulation b. DNA packing c. methylation of DNA d. mRNA processing e. All of the listed responses are correct.

All of the listed responses are correct. All of the listed responses do play a role in the regulation of eukaryotic gene expression.

Which of the following statement(s) about feedback inhibition is/are true? a. It allows a cell to adapt quickly to fluctuations in the availability of important substances. b. The end product of the metabolic pathway controls the activity of the first enzyme in the pathway. c. If the end product accumulates in the cell, the whole pathway is shut down. d. It is common in anabolic pathways. e. All of the listed responses are correct.

All of the listed responses are correct. All of these statements about feedback inhibition are true.

Post-transcriptional controls of gene expression __________. a. may involve regulation of mRNA splicing b. may involve changes to the rate at which an mRNA is translated c. can include translational controls d. can include changes to mRNA stability e. All of the listed responses are correct.

All of the listed responses are correct. Post-transcriptional control can occur at many steps, including mRNA stability, splicing, and translation.

a type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns

Alternative RNA Splicing

a maternal effect gene that codes for a protein responsible for specifying the anterior end in Drosophila melanogaster

Bicoid

a segment of noncoding DNA that helps regulate transcription of a gene by serving as a binding site for a transcription factor; multiple control elements are present in a eukaryotic gene's enhancer

Control Element

a small molecule that binds to a bacterial repressor protein and changes the protein's shape, allowing it to bind to the operator and switch an operon off

Corepressor

cyclic adenosine monophosphate, a ring-shaped molecule made from ATP that is a common intracellular signaling molecule (second messenger) in eukaryotic cells; it is also a regulator of some bacterial operons

Cyclic AMP (cAMP)

a maternal substance, such as a protein or RNA, that when placed into an egg influences the course of early development by regulating the expression of genes that affect the developmental fate of cells

Cytoplasmic Determinant

the presence of methyl groups on the DNA bases (usually cytosine) of plants, animals, and fungi; (The term also refers to the process of adding methyl groups to DNA bases.)

DNA Methylation

the progressive restriction of developmental potential in which the possible fate of each cell becomes more limited as an embryo develops; at the end of determination, a cell is committed to its fate

Determination

the expression of different sets of genes by cells with the same genome

Differential Gene Expression

the process by which a cell or group of cells becomes specialized in structure and function

Differentiation

a gene that helps control the orientation (polarity) of the egg; also called a maternal effect gene

Egg-Polarity Gene

a mutation with a phenotype leading to death of an embryo or larva

Embryonic Lethal

a segment of eukaryotic DNA containing multiple control elements, usually located far from the gene whose transcription it regulates

Enhancer

inheritance of traits transmitted by mechanisms that do not involve the nucleotide sequence

Epigenetic Inheritance

a variant of a bar graph that is made for numeric data by first grouping, or "binning," the variable plotted on the x-axis into intervals of equal width; the "bins" may be integers or ranges of numbers; the height of each bar shows the percent or number of experimental subjects whose characteristics can be described by one of the intervals plotted on the x-axis

Histogram

the attachment of acetyl groups to certain amino acids of histone proteins

Histone Acetylation

any of the master regulatory genes that control placement and spatial organization of body parts in animals, plants, and fungi by controlling the developmental fate of groups of cells

Homeotic Gene

a specific small molecule that binds to a bacterial repressor protein and changes the repressor's shape so that it cannot bind to an operator, thus switching an operon on

Inducer

a process in which a group of cells or tissues influences the development of another group through close-range interactions

Induction

What is the evolutionary significance of alternative RNA splicing? a. It acts as a defense against viral RNA, helping organisms avoid infection, particularly by cancer-causing viruses. b. It expands the number of proteins that can be coded for by one gene, increasing an organism's ability to produce novel proteins. c. Because it is not specific to a cell type, alternative RNA splicing can make sweeping changes in gene expression, allowing an organism to adapt quickly to new situations. d. It can silence genes, giving cells another way of controlling gene expression. e. The introns that are spliced out can become miRNAs and can recognize and degrade mRNA transcripts.

It expands the number of proteins that can be coded for by one gene, increasing an organism's ability to produce novel proteins. Some genes could produce thousands of different proteins from a primary transcript. In most cases, only a few of the possibilities are actually produced. However, different splicing could give rise to novel proteins, some of which could be advantageous.

a gene that, when mutant in the mother, results in a mutant phenotype in the offspring, regardless of the offspring's genotype; maternal effect genes, also called egg-polarity genes, were first identified in Drosophila melanogaster

Maternal Effect Gene

a small, single-stranded RNA molecule, generated from a double-stranded RNA precursor; the miRNA associates with one or more proteins in a complex that can degrade or prevent translation of an mRNA with a complementary sequence

MicroRNA (miRNA)

a substance, such as Bicoid protein in Drosophila, that provides positional information in the form of a concentration gradient along an embryonic axis

Morphogen

the development of the form of an organism and its structures

Morphogenesis

a gene found in viral or cellular genomes that is involved in triggering molecular events that can lead to cancer

Oncogene

in bacterial and phage DNA, a sequence of nucleotides near the start of an operon to which an active repressor can attach; the binding of the repressor prevents RNA polymerase from attaching to the promoter and transcribing the genes of the operon

Operator

a unit of genetic function found in bacteria and phages, consisting of a promoter, an operator, and a coordinately regulated cluster of genes whose products function in a common pathway

Operon

a tumor-suppressor gene that codes for a specific transcription factor that promotes the synthesis of proteins that inhibit the cell cycle

P53 Gene

the development of a multicellular organism's spatial organization, the arrangement of organs and tissues in their characteristic places in three-dimensional space

Pattern Formation

molecular cues that control pattern formation in an animal or plant embryonic structure by indicating a cell's location relative to the organism's body axes; these cues elicit a response by genes that regulate development

Positional Information

a normal cellular gene that has the potential to become an oncogene

Proto-Oncogene

a mechanism for silencing the expression of specific genes; in RNAi, double-stranded RNA molecules that match the sequence of a particular gene are processed into siRNAs that either block translation or trigger the degradation of the gene's messenger RNA; this happens naturally in some cells, and can be carried out in laboratory experiments as well

RNA Interference (RNAi)

a gene that codes for Ras, a G protein that relays a growth signal from a growth factor receptor on the plasma membrane to a cascade of protein kinases, ultimately resulting in stimulation of the cell cycle

Ras Gene

a gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes

Regulatory Gene

a protein that inhibits gene transcription; in prokaryotes, repressors bind to the DNA in or near the promoter; in eukaryotes, repressors may bind to control elements within enhancers, to activators, or to other proteins in a way that blocks activators from binding to DNA

Repressor

one of multiple small, single-stranded RNA molecules generated by cellular machinery from a long, linear, double-stranded RNA molecule; the siRNA associates with one or more proteins in a complex that can degrade or prevent translation of an mRNA with a complementary sequence

Small Interfering RNA (siRNA)

A high rate of gene transcription in eukaryotic cells is usually dependent on __________. a. the binding of general transcription factors to the TATA box within the promoter of a gene b. the coordinated control of genes within operons c. specific binding of activator molecules to enhancers d. protein-protein interactions that are promoted by the activation domains of activator proteins e. The third and fourth listed responses are correct.

The third and fourth listed responses are correct. Specific binding of activator molecules to enhancers and the protein-protein interactions that are promoted by the activation domains of activator proteins equate to elevated rates of gene transcription.

a gene whose protein product inhibits cell division, thereby preventing the uncontrolled cell growth that contributes to cancer

Tumor-Suppressor Gene

a protein that binds to DNA and stimulates gene transcription. In prokaryotes, activators bind in or near the promoter; in eukaryotes, activators generally bind to control elements in enhancers

activator

You have inserted the gene for human growth factor into the E. coli lactose operon, replacing the structural genes with the gene for human growth factor. What substance must you add to your culture of bacteria to cause them to produce human growth factor for you? a. operator protein b. transcription factors c. repressor protein d. allolactose e. human growth factor

allolactose Allolactose will bind to the repressor protein, inactivating it, and allowing transcription of the genes in the operon, including human growth factor.

In prokaryotic genomes, groups of functionally related genes along with their promoters and operators are found together in __________. a. an operon b. an enhancer c. a regulatory gene d. a repressor e. a transcription factor

an operon Putting these related sequences together helps prokaryotes keep related genes under coordinate control.

A bacterium can make the amino acid glycine or absorb it from its surroundings. A biochemist finds that glycine binds to a repressor protein and causes the repressor to bind to the bacterial chromosome, turning off an operon. If it is like other similar operons, the presence of glycine will result in the __________. a. inhibition of bacterial cell division b. production of the repressor protein c. breakdown of glycine d. cessation of the synthesis of glycine e. formation of sex pili

cessation of the synthesis of glycine Because synthesis of glycine requires energy and raw materials, it does not make sense to synthesize it when it is available in the environment.

Which of the following statements is NOT associated with epigenetic inheritance? a. removal of acetyl groups from histones b. DNA phosphorylation c. histone acetylation d. chemical mutagens e. DNA methylation

chemical mutagens By definition, chemical mutagens are chemical agents that can cause an inheritable change in the nucleotide sequence of an organism's DNA. All the other answers are examples of changes made to DNA other than the nucleotide sequence that can affect gene expression and are inheritable.

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. continuous transcription of the operon's genes c. reduced transcription of the operon's genes d. buildup of a substrate for the pathway controlled by the operon e. overproduction of catabolite activator protein (CAP)

continuous transcription of the operon's genes

In eukaryotes, DNA packing seems to affect gene expression primarily by __________. a. allowing unpacked genes to be eliminated from the genome b. protecting DNA from mutations c. controlling access to DNA d. enhancing the recombination of genes e. positioning related genes near each other

controlling access to DNA For example, the genes of tightly packed heterochromatin are usually not transcribed, presumably because RNA polymerase and other necessary proteins can't make contact with the DNA.

Gene expression in bacteria is regulated primarily by __________. a. transcription factors encoded for by mitochondrial DNA b. selectively breaking down the proteins encoded by the genes c. controlling the transcription of genes into mRNA d. controlling the translation of mRNA to produce polypeptides e. controlling gene packing and unpacking

controlling the transcription of genes into mRNA In prokaryotes, most gene expression is regulated by controlling transcription.

Muscle cells differ from nerve cells mainly because they a. express different genes. b. use different genetic codes. c. have unique ribosomes. d. have different chromosomes. e. contain different genes.

express different genes.

The expression of a gene located in a tightly coiled region of DNA can be promoted by __________. a. methylation of histone tails b. the arrival of the RNA polymerase c. removal of acetyl groups from histones d. histone acetylation e. demethylation of DNA

histone acetylation Addition of acetyl groups to the amino acid lysine in the histone tails neutralizes the positive charge of this amino acid so that the histone tails no longer bind to neighboring nucleosomes, thus giving the chromatin a looser structure.

The control of gene expression is more complex in multicellular eukaryotes than in prokaryotes because __________. a. prokaryotes are restricted to stable environments b. eukaryotic cells are much smaller c. many genes of eukaryotes provide information for making polypeptides d. in a multicellular eukaryote, different cells are specialized for different functions e. eukaryotic chromosomes have fewer nucleotides; therefore, each nucleotide sequence must do several jobs

in a multicellular eukaryote, different cells are specialized for different functions Also, eukaryotic cells are more complex than prokaryotic cells.

In some cases, DNA methylation and removal of acetyl groups from histones (i.e., deacetylation) combine to __________. a. remove genomic imprinting b. form a transcription factor c. silence certain genes d. form an enhancer e. turn certain genes on

silence certain genes Both DNA methylation and histone deacetylation tend to repress transcription.

In an inducible operon, the inducer is often the __________ in the pathway being regulated; the inducer binds to the __________, which then becomes __________. a. substrate ... repressor ... active b. substrate ... corepressor ... inactive c. substrate ... repressor ... inactive d. end product ... corepressor ... inactive e. end product ... repressor ... inactive

substrate ... repressor ... inactive The presence of the substrate turns the operon on by binding to the repressor and inactivating it.

Within a cell, the amount of protein made using a given mRNA molecule depends partly on a. the degree of DNA methylation. b. the presence of certain transcription factors. c. the types of ribosomes present in the cytoplasm. d. the number of introns present in the mRNA. e. the rate at which the mRNA is degraded.

the rate at which the mRNA is degraded.

Which of the following is an example of post-transcriptional control of gene expression? a. gene amplification contributing to cancer b. the removal of introns and alternative splicing of exons c. the addition of methyl groups to cytosine bases of DNA d. the binding of transcription factors to a promoter e. the folding of DNA to form heterochromatin

the removal of introns and alternative splicing of exons

Both repressible and inducible operons control gene expression at the level of __________. a. transcription b. translation c. post-transcriptional processing d. post-translational processing e. DNA packing

transcription The repressors that attach to operators act to block transcription.

The functioning of enhancers is an example of a. post-translational control that activates certain proteins. b. a eukaryotic equivalent of prokaryotic promoter functioning. c. transcriptional control of gene expression. d. a post-transcriptional mechanism to regulate mRNA. e. the stimulation of translation by initiation factors.

transcriptional control of gene expression.