GCD 3033 Chapter 8 Practice Quiz

Although all of the steps involved in expressing a gene can in principle be regulated, for most genes the most important point of control is: A. transcription initiation. B. RNA processing. C. RNA transport and localization. D. mRNA degradation. E. mRNA translation.

A

MicroRNAs ____________________. A. are produced from a precursor miRNA transcript B. are found only in humans C. control gene expression by base-pairing with DNA sequences D. can degrade RNAs by using their intrinsic catalytic activity

A

The extent of complementarity of a miRNA with its target mRNA determines ___________________________. A. whether the mRNA will be degraded or transported elsewhere in the cell B. whether the mRNA will be transported to the nucleus C. whether RISC is degraded D. whether the miRNA synthesizes a complementary strand

A

When a gene regulatory protein binds to DNA, its most important interactions occur with which parts of the DNA? A. base pairs B. sugar groups in the DNA backbone C. phosphate groups in the DNA backbone

A

Which of the following statements about transcriptional regulators is false? A.Transcriptional regulators usually interact with the sugar-phosphate backbone on the outside of the double helix to determine where to bind on the DNA helix. B. Transcriptional regulators will form hydrogen bonds, ionic bonds, and hydrophobic interactions with DNA. C. The DNA-binding motifs of transcriptional regulators usually bind in the major groove of the DNA helix. D. The binding of transcriptional regulators generally does not disrupt the hydrogen bonds that holds the double helix together.

A

You are studying a set of mouse genes whose expression increases when cells are exposed to the hormone cortisol, and you believe that the same cortisol-responsive transcriptional activator regulates all of these genes. Which of the following statements below should be true if your hypothesis is correct? A. The cortisol-responsive genes share a DNA sequence in their regulatory regions that binds the cortisol-responsive transcriptional activator. B. The cortisol-responsive genes must all be in an operon. C. The transcriptional regulators that bind to the regulatory regions of the cortisol-responsive genes must all be the same. D. The cortisol-responsive genes must not be transcribed in response to other hormones.

A

In bacteria, if a protein binds to the ribosomal binding site on an mRNA, what is the consequence? A. The small ribosomal subunit will not be able to bind to the mRNA, and translation will be inhibited. B. The protein will recruit the small ribosomal subunit to the mRNA, increasing translation efficiency. C. The ribosome will begin translation at a new location on the mRNA.

A.

A typical differentiated human cell will express how many of its approximately 25,000 genes? A. About 1000 genes B. From 5000 to 15,000 genes C. All 25,000 genes

B

Combinatorial control of gene expression __________________________. A. involves every gene using a different combination of transcriptional regulators for its proper expression B. involves groups of transcriptional regulators working together to determine the expression of a gene C. involves only the use of gene activators used together to regulate genes appropriately D. is seen only when genes are arranged in operons

B

How are most eucaryotic transcription regulators able to affect transcription when their binding sites are far from the promoter? A. by binding to their binding site and sliding to the site of RNA polymerase assembly B. by looping out the intervening DNA between their binding site and the promoter C. by unwinding the DNA between their binding site and the promoter D. by attracting RNA polymerase and modifying it before it can bind to the promoter

B

Investigators performed nuclear transplant experiments to determine whether DNA is altered irreversibly during development. Which of the following statements about these experiments is true? A. Because the donor nucleus is taken from an adult animal, the chromosomes from the nucleus must undergo recombination with the DNA in the egg for successful development to occur. B. The embryo that develops from the nuclear transplant experiment is genetically identical to the donor of the nucleus. C. The meiotic spindle of the egg must interact with the chromosomes of the injected nuclei for successful nuclear transplantation to occur. D. Although nuclear transplantation has been successful in producing embryos in some mammals with the use of foster mothers, evidence of DNA alterations during differentiation has not been obtained for plants.

B

The distinct characteristics of different cell types in a multicellular organism result mainly from the differential regulation of the _________________. A. replication of specific genes B. transcription of genes transcribed by RNA polymerase II C. transcription of housekeeping genes D. packing of DNA into nucleosomes in some cells and not others

B

The tryptophan operator ___________________________. A. is an allosteric protein B. binds to the tryptophan repressor when the repressor is bound to tryptophan C. is required for production of the mRNA encoded by the tryptophan operon D. is important for the production of the tryptophan repressor

B

What is the definition of an operon? A. A short sequence of DNA to which a gene regulatory protein binds. B. A set of genes (found in bacteria but not eucaryotes) that is transcribed into a single mRNA. C. A gene that is controlled by the binding of two or more gene regulatory proteins.

B

What type of molecule triggers RNA interference (RNAi)? A. Foreign, single-stranded DNA B. Foreign, double-stranded RNA C. Foreign DNA-RNA hybrids

B

Which is NOT an example of epigenetic inheritance? A. The inheritance of methylation patterns in DNA B. The inheritance of a single nucleotide mutation in a gene C. The inheritance of patterns of chromosome condensation D. The inheritance of a regulatory protein that activates its own transcription

B

Which is not involved in post-trancriptional control? A. Riboswitch B. DNA methylation C. mircoRNA D. RNA interference

B

Which of the following describes the lac operon in E. coli when both lactose and glucose are present in the culture medium? A. CAP and the lac repressor are both bound to the lac operon's regulatory DNA, and the lac operon is not expressed. B. Neither CAP nor the lac repressor is bound to the lac operon's regulatory DNA, and the lac operon is not expressed. C. CAP, but not the lac repressor, is bound to the lac operon's regulatory DNA, and the lac operon is expressed. D. The lac repressor, but not CAP, is bound to the lac operon's regulatory DNA, and the lac operon is not expressed.

B

Which of the following statements about RNAi is true? A. The RNAi mechanism is found only in plants and animals. B. RNAi is induced when double-stranded RNA is present in the cell. C. RISC uses the siRNA duplex to locate complementary foreign RNA molecules. D. siRNAs bind to miRNAs to induce RNAi.

B

Which of the following statements about riboswitches is false? A. Riboswitches can block the production of mRNAs. B. Riboswitches can control the translation of mRNAs. C. Riboswitches are made from rRNAs. D. Riboswitches can bind metabolites.

B

Which of the following statements about the Ey transcriptional regulator is false? A. Expression of Ey in cells that normally form legs in the fly will lead to the formation of an eye in the middle of the legs. B. The Ey transcription factor must bind to the promoter of every eye-specific gene in the fly. C. Positive feedback loops ensure that Ey expression remains switched on in the developing eye. D. A homolog of Ey is found in vertebrates; this homolog is also used during eye development.

B

Which of the following statements is NOT true about the differences between liver cells and kidney cells in the same organism? A. They contain the same genes, but express them differently. B. They contain different genes. C. They contain different sets of proteins.

B

In bacteria when transcription regulators bind to regulatory DNA sequences close to where RNA polymerase binds, they: A. activate transcription of the gene B. repress transcription of the gene C. activate or repress transcription of the gene depending upon where they are located relative to the promoter D. activate or repress transcription of the gene depending upon their concentration

C

In eucaryotes, where do transcription regulators bind? A. Upstream from a gene B. Downstream from a gene C. Either upstream or downstream from a gene D. The TATA box

C

In the bacterial cell, the trytophan operon encodes the genes needed to synthesize tryptophan. When the concentration of tryptophan inside the cell is high: A. it inactivates the tryptophan repressor allowing transcription of the tryptophan operon. B. it inactivates the tryptophan repressor which shuts down the tryptophan operon. C. it activates tryptophan repressor which shuts down the tryptophan operon.

C

Operons ___________________________. A. are commonly found in eucaryotic cells B. are transcribed by RNA polymerase II C. contain a cluster of genes transcribed as a single mRNA D. can only be regulated by gene activator proteins

C

The MyoD transcriptional regulator is normally found in differentiating muscle cells and participates in the transcription of genes that produce muscle-specific proteins, such as those needed in contractile tissue. Amazingly, expression of MyoD in fibroblasts causes these cells derived from skin connective tissue to produce proteins normally only seen in muscles. However, some other cell types do not transcribe muscle-specific genes when MyoD is expressed in them. Which of the following statements below is the best explanation of why MyoD can cause fibroblasts to express muscle-specific genes? A. Unlike some other cell types, fibroblasts have not lost the muscle-specific genes from their genome. B. The muscle-specific genes must be in heterochromatin in fibroblasts. C. During their developmental history, fibroblasts have accumulated some transcriptional regulators in common with differentiating muscle cells. D. The presence of MyoD is sufficient to activate the transcription of muscle-specific genes in all cell types.

C

The human genome encodes about 24,000 genes. Approximately how many genes does the typical differentiated human cell express at any one time? A. 24,000—all of them B. between 21,500 and 24,000—at least 90% of the genes C. between 5000 and 15,000 D. less than 2500

C

What is a riboswitch? A. A small molecule that regulates the translation of specific mRNAs. B. A gene regulatory protein that turns on the expression of ribosomal proteins. C. An mRNA that can regulate its own transcription and translation.

C

What is the ultimate fate of an mRNA that is targeted by a microRNA (miRNA) based on their complementary nucleotide sequences? A. The mRNA will be translated more efficiently by ribosomes. B. The mRNA will be transported to the nucleus. C. The mRNA will be destroyed by a nuclease. D. The mRNA will be excreted from the cell.

C

Which of the following cell types, when fully differentiated, does NOT divide to form new cells? A. Fibroblasts B. Liver cells C. Neurons B. Smooth muscle cells

C

Which of the following describes the lac operon in E. coli when lactose, but not glucose, is present in the culture medium? A. CAP and the lac repressor are both bound to the lac operon's regulatory DNA, and the lac operon is not expressed. B. Neither CAP nor the lac repressor is bound to the lac operon's regulatory DNA, and the lac operon is not expressed. C. CAP, but not the lac repressor, is bound to the lac operon's regulatory DNA, and the lac operon is expressed. D. The lac repressor, but not CAP, is bound to the lac operon's regulatory DNA, and the lac operon is not expressed.

C

Which of the following is false? A. Eucaryotic gene activator proteins stimulate transcription initiation by recruiting proteins that modify chromatin structure. B. Eucaryotic gene activator proteins stimulate transcription initiation by aiding in the assembly of general transcription factors and RNA polymerase at the promoter. C. Eucaryotic gene activator proteins stimulate transcription initiation by recruiting a DNA polymerase to the promoter.

C

Which of the following is not involved in post-transcriptional control? A. the spliceosome B. dicer C. mediator D. RISC

C

Which of the following is the initiation site in a gene? A. The part of a promoter where transcription factors bind to begin B. The part of a promoter where RNA polymerase first binds C. The part of a promoter where transcription actually begins

C

Which of the following statements about miRNAs is false? A. One miRNA can regulate the expression of many genes. B. miRNAs are transcribed in the nucleus from genomic DNA. C. miRNAs are produced from rRNAs. D. miRNAs are made by RNA polymerase.

C

Which of the following statements accurately describes the expression of the repressor protein of the tryptophan operon? A. The gene for the tryptophan repressor is turned on in response to high levels of tryptophan in the cell. B. The gene for the tryptophan repressor is turned off in response to high levels of tryptophan in the cell. C. The gene for the tryptophan repressor is expressed constitutively.

C

Which form of post-translational control is being exploited by scientists to inactivate genes of interest? A. Riboswitch B. DNA methylation C. microRNA D. RNA interference

D

Which of the following statements about DNA methylation in eucaryotes is false? A. Appropriate inheritance of DNA methylation patterns involves maintenance methyltransferase. B. DNA methylation involves a covalent modification of cytosine bases. C. Methylation of DNA attracts proteins that block gene expression. D. Immediately after DNA replication, each daughter helix contains one methylated DNA strand, which corresponds to the newly synthesized strand.

D

Which of the following statements about differentiated cells is true? A. Cells of distinct types express nonoverlapping sets of transcription factors. B. Once a cell has differentiated, it can no longer change its gene expression. C. Once a cell has differentiated, it will no longer need to transcribe RNA. D. Some of the proteins found in differentiated cells are found in all cells of a multicellular organism.

D

How many different gene regulatory proteins work together to control a typical human gene?

Dozens

Different cell types that respond to the same hormone usually turn on the same sets of genes. True or False...

False

Differentiated cells in multicellular organisms require hormonal input to 'remember' what type of cell they should be. True or False...

False

The general transcription factors that assemble at a eucaryotic promoter are different, depending on the specific gene being transcribed by polymerase II. True or False...

False

When a gene regulatory protein binds to DNA, it typically disrupts the hydrogen bonding between base pairs. True or False...

False

translation control: step 3 transcriptional control: step 1 RNA processing control: step 2 protein activity control: step 4

In principle, a eucaryotic cell can regulate gene expression at any step in the pathway from DNA to the active protein. Match each of the types of control, listed below, with the appropriate step (labeled 1-4) in the diagram.

A gene regulatory protein usually binds to which groove in the DNA double helix?

Major groove

activator protein: 1 RNA polymerase: 4 general transcription factors: 3 mediator: 2

Match each term (a-d) with the corresponding structure (1-4) in the figure.

A cell can change the expression of its genes in response to external signals. True or False...

True

A single transcription regulator, if expressed in the appropriate precursor cell, can trigger the formation of a specialized cell type or even an entire organ. True or False...

True

Even though control of eucaryotic gene expression is combinatorial, the effect of a single gene regulatory protein can still be decisive in switching any particular gene on or off. True or False...

True

In principle, how many different cell types can an organism having four different types of transcription regulator and thousands of genes create?

up to 16