Chapter 16: Control Of Gene Expression

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Chapter 16: Control Of Gene Expression - Quiz

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Questions and Answers
  • 1. 

    The most common form of regulation in bacteria and eukaryotes is

    • A.

      Transcriptional control.

    • B.

      Translational control.

    • C.

      Promotor control.

    • D.

      Repressor control.

    • E.

      Operator control.

    Correct Answer
    A. Transcriptional control.
    Explanation
    Transcriptional control refers to the regulation of gene expression at the level of transcription, where the DNA is transcribed into RNA. This form of regulation is the most common in both bacteria and eukaryotes. It involves the binding of specific transcription factors to the promoter region of genes, either enhancing or inhibiting the binding of RNA polymerase and thus influencing the rate of transcription. Transcriptional control allows cells to quickly respond to changes in their environment and regulate the production of specific proteins as needed.

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  • 2. 

    Transcriptional control-proteins increase the rate of transcription by binding to

    • A.

      MRNA sequences within the DNA.

    • B.

      TRNA sequences within the DNA.

    • C.

      Operator sequences within the DNA.

    • D.

      Promotor sequences within the DNA.

    • E.

      Enhancer sequences within the DNA.

    Correct Answer
    E. Enhancer sequences within the DNA.
    Explanation
    Transcriptional control proteins increase the rate of transcription by binding to enhancer sequences within the DNA. Enhancer sequences are specific DNA sequences that are located near the promoter region of a gene. When transcriptional control proteins bind to these enhancer sequences, they can enhance the binding of RNA polymerase to the promoter region, leading to an increased rate of transcription. This allows for the regulation of gene expression and the production of specific proteins in response to various cellular signals and environmental conditions.

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  • 3. 

    All regulatory proteins have common DNA binding motifs, which are particular bends in their protein chains that permit them to interlock with the

    • A.

      Minor groove of the DNA helix.

    • B.

      Major groove of the DNA helix.

    • C.

      Outside groove of the DNA helix.

    • D.

      Inside groove of the DNA helix.

    • E.

      Hydrogen bonding groove of the DNA helix.

    Correct Answer
    B. Major groove of the DNA helix.
    Explanation
    Regulatory proteins have common DNA binding motifs that allow them to interact with the major groove of the DNA helix. The major groove provides a larger space and more specific chemical groups compared to the minor groove, making it more favorable for protein-DNA interactions. By binding to the major groove, regulatory proteins can recognize specific DNA sequences and control gene expression. The other options, such as the minor groove, outside groove, inside groove, or hydrogen bonding groove, do not accurately describe the location where regulatory proteins bind to DNA.

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  • 4. 

    Vertebrate cells apparently possess a protein that by binding to clusters of 5-methylcytosine ensures that the bound gene will stay in the "off" position. This control on the role of gene regulation is a result of

    • A.

      Translation.

    • B.

      Enhancer expression.

    • C.

      Methylation.

    • D.

      Promotor expression.

    • E.

      Operator suppression.

    Correct Answer
    C. Methylation.
    Explanation
    The correct answer is methylation. Methylation refers to the addition of a methyl group to the DNA molecule, specifically to the cytosine base. In vertebrate cells, this methylation process helps in gene regulation by binding to clusters of 5-methylcytosine, which ensures that the bound gene remains in the "off" position. Methylation acts as a control mechanism for gene expression, as it can prevent the transcription machinery from accessing the gene and initiating gene expression.

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  • 5. 

    Regulatory proteins shut off transcription by binding to a site immediately in front of the promoter and often even overlapping the promotor. This site is referred to as the

    • A.

      Suppressor site.

    • B.

      Operator site.

    • C.

      Repressor site.

    • D.

      Regulatory site.

    • E.

      Transcriptional control site.

    Correct Answer
    B. Operator site.
    Explanation
    Regulatory proteins shut off transcription by binding to a site immediately in front of the promoter and often even overlapping the promoter. This site is referred to as the operator site. The operator site is a DNA sequence that acts as a binding site for regulatory proteins called repressors. When a repressor protein binds to the operator site, it prevents RNA polymerase from binding to the promoter and initiating transcription. Therefore, the operator site plays a crucial role in regulating gene expression by controlling the access of RNA polymerase to the promoter region.

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  • 6. 

    Histones are tightly packed into ______, which are located within the DNA.

    • A.

      Operons

    • B.

      Nucleosomes

    • C.

      Clusters of proteins

    • D.

      Repressor genes

    • E.

      Facilitators sites

    Correct Answer
    B. Nucleosomes
    Explanation
    Histones are proteins that help in organizing and packing DNA within the nucleus of a cell. They are tightly packed together to form structures called nucleosomes. Nucleosomes consist of DNA wrapped around a core of histone proteins. These nucleosomes play a crucial role in regulating gene expression and protecting DNA from damage. Therefore, the correct answer is nucleosomes.

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  • 7. 

    Which of the following is the hallmark of multicellular organisms?

    • A.

      Grow and divide rapidly

    • B.

      Cells adjust quickly to outside environment

    • C.

      Homeostasis

    • D.

      Quickly synthesize amount and type of enzymes according to available nutrients

    • E.

      Respond by gene action to oxygen availability

    Correct Answer
    C. Homeostasis
    Explanation
    Homeostasis is the hallmark of multicellular organisms. It refers to the ability of an organism to maintain a stable internal environment despite changes in the external environment. This is achieved through various mechanisms such as temperature regulation, pH balance, and nutrient balance. Homeostasis is essential for the proper functioning of cells and organ systems in multicellular organisms, allowing them to survive and thrive in different conditions.

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  • 8. 

    Enhancers are the binding sites for the

    • A.

      Promotors of DNA synthesis.

    • B.

      Suppressor factors.

    • C.

      Co-activation factors.

    • D.

      Mediator factors.

    • E.

      Specific transcription factors.

    Correct Answer
    E. Specific transcription factors.
    Explanation
    Enhancers are DNA sequences that enhance the transcription of specific genes. They act by binding to specific transcription factors, which are proteins that regulate gene expression. These transcription factors can activate or repress gene transcription by binding to the promoter region of the gene. Therefore, the correct answer is specific transcription factors, as enhancers bind to these factors to regulate gene expression.

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  • 9. 

    The most common form of control of gene expression in both the prokaryotic and eukaryotic organisms is

    • A.

      RNA processing control.

    • B.

      Translational control.

    • C.

      Protein phosphorylation control.

    • D.

      Transcriptional control.

    • E.

      MRNA degradation control.

    Correct Answer
    D. Transcriptional control.
    Explanation
    Transcriptional control is the most common form of gene expression control in both prokaryotic and eukaryotic organisms. This process involves the regulation of gene expression at the level of transcription, where the DNA sequence is transcribed into RNA. Transcriptional control can be achieved through various mechanisms such as the binding of transcription factors to DNA, chromatin remodeling, and the action of regulatory proteins. This form of control allows the organism to regulate which genes are transcribed and therefore influences the overall gene expression profile.

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  • 10. 

    A nucleosome contains ____ histones within its core.

    • A.

      2

    • B.

      4

    • C.

      6

    • D.

      8

    • E.

      64

    Correct Answer
    D. 8
    Explanation
    A nucleosome contains 8 histones within its core. Histones are proteins that help in the packaging of DNA into a compact structure called chromatin. Each nucleosome consists of a core particle made up of 8 histone proteins, with DNA wrapped around it. The histones play a crucial role in regulating gene expression and maintaining the integrity of the DNA molecule.

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  • 11. 

    The basic tool of genetic regulation is the ability of certain proteins to bind to specific

    • A.

      Regulatory RNA sequences.

    • B.

      Regulatory DNA sequences.

    • C.

      Repressor parts of the gene.

    • D.

      Promoter parts of the gene.

    • E.

      Enzymes of the cell.

    Correct Answer
    B. Regulatory DNA sequences.
    Explanation
    The correct answer is regulatory DNA sequences. Genetic regulation involves controlling the expression of genes, and this is primarily achieved through the binding of proteins to specific regulatory DNA sequences. These sequences, often found in the promoter region of a gene, help determine whether the gene is turned on or off, and play a crucial role in regulating gene expression. By binding to these regulatory DNA sequences, proteins can either enhance or inhibit the transcription of the gene, thereby controlling the production of the corresponding protein.

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  • 12. 

    Which of the following is not true about control of gene expression?

    • A.

      In bacteria it allows them to adapt to changing environments.

    • B.

      In multicellular organisms it is critical for development.

    • C.

      In bacteria it allows them to replicate without control.

    • D.

      In multicellular organisms it allows them to maintain homeostasis.

    • E.

      In multicellular organisms it allows them to function as a whole.

    Correct Answer
    C. In bacteria it allows them to replicate without control.
    Explanation
    Control of gene expression in bacteria is crucial for their adaptation to changing environments, as mentioned in the first statement. In multicellular organisms, it plays a critical role in development, maintenance of homeostasis, and functioning as a whole. However, the statement that control of gene expression in bacteria allows them to replicate without control is not true. Bacteria also regulate their gene expression to ensure proper replication and growth.

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  • 13. 

    RNA polymerase binds to a site on DNA called the

    • A.

      Operator.

    • B.

      Repressor.

    • C.

      Footprint.

    • D.

      Promoter.

    • E.

      Operon.

    Correct Answer
    D. Promoter.
    Explanation
    RNA polymerase is an enzyme responsible for the synthesis of RNA from a DNA template. It binds to a specific site on DNA called the promoter to initiate transcription. The promoter region contains specific sequences that signal the start of a gene and provide a binding site for RNA polymerase. The other options, such as operator, repressor, footprint, and operon, are not directly involved in the initiation of transcription by RNA polymerase.

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  • 14. 

    Proteins that bind to regulatory sequences have shapes that fit into the

    • A.

      Promoter.

    • B.

      Operator.

    • C.

      Operon.

    • D.

      Minor groove of DNA.

    • E.

      Major groove of DNA.

    Correct Answer
    E. Major groove of DNA.
    Explanation
    Proteins that bind to regulatory sequences, such as transcription factors, interact with DNA through specific binding sites. The DNA molecule has two grooves, the major groove and the minor groove, which are formed by the arrangement of the nucleotide bases. The major groove provides a larger and more accessible space for protein binding compared to the minor groove. Therefore, proteins that bind to regulatory sequences have shapes that fit into the major groove of DNA, allowing them to accurately recognize and bind to their target sequences.

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  • 15. 

    The DNA-binding proteins of almost all regulatory proteins employ one of a small set of shapes that enable them to fit into the major groove of DNA. These shapes are called

    • A.

      Structural motifs.

    • B.

      DNA prints.

    • C.

      Operons.

    • D.

      Repressors.

    • E.

      Transcriptional domains.

    Correct Answer
    A. Structural motifs.
    Explanation
    The correct answer is "structural motifs". DNA-binding proteins use specific shapes called structural motifs to fit into the major groove of DNA. These motifs allow the proteins to interact with DNA and regulate gene expression. The other options, such as DNA prints, operons, repressors, and transcriptional domains, are not directly related to the shapes used by DNA-binding proteins to bind to DNA.

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  • 16. 

    All of the following are examples of shapes in regulatory proteins which are used to bind to DNA except the

    • A.

      Zinc finger.

    • B.

      TATA box.

    • C.

      Helix-turn-helix.

    • D.

      Leucine zipper.

    Correct Answer
    B. TATA box.
    Explanation
    The TATA box is not an example of a shape in regulatory proteins used to bind to DNA. The zinc finger, helix-turn-helix, and leucine zipper are all examples of structural motifs found in regulatory proteins that are involved in DNA binding. The TATA box, on the other hand, is a DNA sequence found in the promoter region of genes that is recognized by transcription factors, but it is not a shape or structural motif in a protein.

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  • 17. 

    In gene regulation, negative control is exerted by a(n)

    • A.

      Activator.

    • B.

      Operon.

    • C.

      Promoter.

    • D.

      Regulator.

    • E.

      Repressor.

    Correct Answer
    E. Repressor.
    Explanation
    In gene regulation, negative control is exerted by a repressor. A repressor is a protein that binds to the operator region of the DNA, preventing the transcription of the gene. This binding inhibits the binding of RNA polymerase to the promoter region, thereby preventing the initiation of transcription. By blocking the expression of a gene, the repressor negatively controls gene regulation.

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  • 18. 

    In gene regulation, a gene is "turned on" by a(n)

    • A.

      Activator.

    • B.

      Stimulator.

    • C.

      Promoter.

    • D.

      Regulator.

    • E.

      Repressor.

    Correct Answer
    A. Activator.
    Explanation
    In gene regulation, a gene is "turned on" by an activator. Activators are proteins that bind to specific DNA sequences near the gene and enhance the transcription process. They can recruit other proteins, such as RNA polymerase, to the gene's promoter region, leading to increased gene expression. Activators play a crucial role in regulating gene expression and controlling various cellular processes.

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  • 19. 

    A bacterial gene regulatory system is likely to have all of the following except

    • A.

      A coding sequence.

    • B.

      An operator.

    • C.

      A promoter.

    • D.

      One of more introns.

    • E.

      A ribosome recognition site.

    Correct Answer
    D. One of more introns.
    Explanation
    A bacterial gene regulatory system is unlikely to have one or more introns. Introns are non-coding regions of DNA that are typically found in eukaryotic genes, but not in bacterial genes. Bacterial genes are typically composed of a coding sequence, which contains the information for protein synthesis, an operator, which controls the expression of the gene, a promoter, which initiates transcription, and a ribosome recognition site, which allows for the binding of ribosomes during translation. Therefore, the absence of introns is a characteristic feature of bacterial gene regulatory systems.

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  • 20. 

    Small RNAs can regulate gene expression. One type, called micro RNA (miRNA), acts by binding directly to

    • A.

      MRNA to prevent translation.

    • B.

      TRNA to prevent transcription.

    • C.

      MRNA to prevent transcription.

    • D.

      TRNA to prevent translation.

    Correct Answer
    A. MRNA to prevent translation.
    Explanation
    Micro RNA (miRNA) is a type of small RNA that regulates gene expression by binding directly to mRNA. This binding prevents the translation of mRNA into protein, thus inhibiting gene expression. It does not bind to tRNA or prevent transcription, as these processes are not involved in the regulation of gene expression by miRNA.

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  • 21. 

    Which of the following must happen for transcription to be initiated?

    • A.

      DNA polymerase must have access to the DNA double helix and also must be capable of binding to the gene's promoter.

    • B.

      RNA polymerase must have access to the DNA double helix and also must be capable of binding to the gene's promoter.

    • C.

      DNA polymerase must have access to the RNA and also must be capable of binding to the gene's promoter.

    • D.

      DNA ligase must have access to the DNA double helix and also must be capable of binding to the gene's promoter.

    • E.

      DNA kinase must have access to the DNA double helix and also must be capable of binding to the gene's promoter.

    Correct Answer
    B. RNA polymerase must have access to the DNA double helix and also must be capable of binding to the gene's promoter.
    Explanation
    For transcription to be initiated, RNA polymerase must have access to the DNA double helix and be capable of binding to the gene's promoter. Transcription is the process of synthesizing RNA from a DNA template, and it is carried out by RNA polymerase. The RNA polymerase recognizes and binds to the promoter region on the DNA, which signals the start of transcription. It then unwinds the DNA double helix and begins to synthesize the RNA molecule using the DNA template. Therefore, the correct answer is that RNA polymerase must have access to the DNA double helix and be capable of binding to the gene's promoter.

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  • 22. 

    When E. coli cells produce the amino acid tryptophan, a cluster of five genes is transcribed together. This cluster of genes is referred to as the

    • A.

      Trp transcriptional operator.

    • B.

      Trp regulator.

    • C.

      Trp suppressor.

    • D.

      Trp operon.

    • E.

      Trp promoter.

    Correct Answer
    D. Trp operon.
    Explanation
    The correct answer is "trp operon." In prokaryotes like E. coli, an operon is a group of genes that are transcribed together and regulated by a single promoter. The trp operon consists of a cluster of five genes involved in tryptophan biosynthesis, and they are transcribed together as a single mRNA molecule. The trp operon also contains an operator region that controls the transcription of these genes in response to the presence or absence of tryptophan. Therefore, "trp operon" is the appropriate term to describe this cluster of genes.

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  • 23. 

    The proteins necessary for the use of lactose in E. coli are collectively called the

    • A.

      Lac regulator.

    • B.

      Lac suppressor.

    • C.

      Lac operon.

    • D.

      Lac promoter.

    • E.

      Lac transcriptional operator.

    Correct Answer
    C. Lac operon.
    Explanation
    The proteins necessary for the use of lactose in E. coli are collectively called the lac operon. The lac operon is a group of genes that are responsible for the metabolism of lactose in E. coli. It includes the genes lacZ, lacY, and lacA, which encode for the enzymes necessary for lactose metabolism. The lac operon also includes a promoter region, which is responsible for initiating the transcription of the genes, and an operator region, which controls the expression of the genes. Together, these components make up the lac operon, which regulates the use of lactose in E. coli.

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  • 24. 

    Eukaryotic organisms

    • A.

      Have their transcription occurring in the cytoplasm and translation in the nucleus.

    • B.

      Have their transcription occurring in the nucleus and translation in the cytoplasm.

    • C.

      Have only operons to assist in gene expression.

    • D.

      Carry out protein synthesis only in the presence of the cAMP molecule.

    • E.

      Use the leucine zipper primarily for the production of the amino acid tryptophan.

    Correct Answer
    B. Have their transcription occurring in the nucleus and translation in the cytoplasm.
    Explanation
    Eukaryotic organisms have their transcription occurring in the nucleus and translation in the cytoplasm. In eukaryotic cells, the DNA is located within the nucleus, where transcription takes place. During transcription, the DNA is transcribed into messenger RNA (mRNA). The mRNA then exits the nucleus and enters the cytoplasm, where translation occurs. Translation is the process of synthesizing proteins using the information encoded in the mRNA. This process takes place on ribosomes in the cytoplasm. Therefore, the correct answer is that eukaryotic organisms have their transcription occurring in the nucleus and translation in the cytoplasm.

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  • 25. 

    Which of the following statements regarding primary transcripts in eukaryotes is correct?

    • A.

      The primary transcript is composed of RNA polymerase and associated histones.

    • B.

      The primary transcript has the exons removed and the introns retained for translation.

    • C.

      The primary transcript is a faithful copy of the entire gene including exons and introns.

    • D.

      The primary transcript is a faithful copy of the gene, but the introns have been removed.

    • E.

      The primary transcript is a faithful copy, but the exons have been removed.

    Correct Answer
    C. The primary transcript is a faithful copy of the entire gene including exons and introns.
    Explanation
    The primary transcript in eukaryotes is a faithful copy of the entire gene, including both exons and introns. This means that it contains all the coding regions (exons) as well as the non-coding regions (introns) of the gene. This primary transcript is then processed to remove the introns and join the exons together, resulting in the mature messenger RNA (mRNA) molecule that can be translated into protein. Therefore, the correct statement is that the primary transcript includes both exons and introns.

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  • 26. 

    The enzyme -galactosidase acts on lactose to form galactose. In turn, the presence of galactose leads to expression of the enzymes responsible for the metabolism of galactose. In this case, lactose is serving as a carbon source and as a(n)

    • A.

      Inducer.

    • B.

      Repressor.

    • C.

      Effector.

    • D.

      Operon.

    Correct Answer
    A. Inducer.
    Explanation
    Lactose acts as an inducer in this case because it triggers the expression of enzymes responsible for the metabolism of galactose. The enzyme -galactosidase breaks down lactose into galactose, and the presence of galactose then leads to the expression of the enzymes needed to metabolize it. Therefore, lactose acts as an inducer by initiating the expression of these enzymes.

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  • 27. 

    Which of the following statements regarding control of the lac operon and lactose utilization in bacteria is false?

    • A.

      The lac operon will not be induced in the presence of both glucose and lactose.

    • B.

      Control of the lac operon is negative, mediated by a repressor.

    • C.

      The lac operon controls the expression of three downstream genes.

    • D.

      Bacteria preferentially utilize lactose as a carbon source.

    Correct Answer
    D. Bacteria preferentially utilize lactose as a carbon source.
    Explanation
    The given statement is false because bacteria do not preferentially utilize lactose as a carbon source. In the presence of both glucose and lactose, bacteria will first utilize glucose as the preferred carbon source before utilizing lactose. This phenomenon is known as catabolite repression. The lac operon is responsible for the metabolism of lactose when glucose is not available, and its control is negative, mediated by a repressor protein. The lac operon controls the expression of three downstream genes involved in lactose metabolism.

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  • 28. 

    You are studying the regulation of a prokaryotic operon. Experimental results suggest that the operon is governed by negative control. Based on this information, you conclude that

    • A.

      The operon is ON in the absence of its regulatory protein.

    • B.

      The operon is OFF in the absence of its regulatory protein.

    • C.

      The presence of an inducer will always cause a repressor to bind the operator.

    • D.

      The presence of an inducer will always prevent a repressor from binding the operator.

    Correct Answer
    A. The operon is ON in the absence of its regulatory protein.
    Explanation
    Based on the information provided, if the operon is governed by negative control, it means that the regulatory protein acts as a repressor, preventing transcription of the operon. Therefore, in the absence of the regulatory protein, the operon would be "ON" and transcription would occur.

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