Operon Model Trivia Quiz Ch 18
- 1.
What does the operon model attempt to explain?
- A.
Bacterial resistance to antibiotics
- B.
How genes move between homologous regions of DNA
- C.
The coordinated control of gene expression in bacteria
- D.
The mechanism of viral attachment to a host cell
- E.
Horizontal transmission of plant viruses
Correct Answer
C. The coordinated control of gene expression in bacteriaExplanation
The operon model attempts to explain the coordinated control of gene expression in bacteria. In bacteria, genes are often organized into operons, which are clusters of genes that are transcribed together as a single mRNA molecule. The operon model describes how the expression of these genes is regulated by a common regulatory region called the operator. This allows bacteria to control the expression of multiple genes involved in a specific biological process or pathway in a coordinated manner.Rate this question:
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- 2.
The role of a metabolite that controls a repressible operon is to
- A.
Bind to the promoter region and decrease the affinity of RNA polymerase for the promoter
- B.
Bind to the repressor protein and activate it
- C.
Bind to the repressor protein and inactivate it
- D.
Bind to the operator region and block the attachment of RNA polymerase to the promoter
- E.
Increase the production of inactive repressor proteins
Correct Answer
B. Bind to the repressor protein and activate itExplanation
The correct answer is that the metabolite binds to the repressor protein and activates it. This means that the metabolite molecule interacts with the repressor protein, causing a conformational change that allows the repressor protein to bind to the operator region of the operon. By binding to the operator, the repressor prevents RNA polymerase from attaching to the promoter region and initiating transcription. Therefore, the metabolite indirectly controls the expression of the operon by activating the repressor protein.Rate this question:
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- 3.
The tryptophan operon is a repressible operon that is
- A.
Permanently turned on
- B.
Turned on only when typtophan is present in the growth medium
- C.
Turned on only when glucose is present in the growth medium
- D.
Turned off whenever tryptophan is added to the growth medium
- E.
Turned off only when glucose is present in the growth medium
Correct Answer
D. Turned off whenever tryptophan is added to the growth mediumExplanation
The tryptophan operon is a repressible operon, meaning that it is usually turned on and producing enzymes involved in tryptophan synthesis. However, when tryptophan is added to the growth medium, it acts as a co-repressor and binds to the repressor protein, forming an active repressor complex. This complex then binds to the operator region of the operon, preventing transcription of the genes involved in tryptophan synthesis. Therefore, the operon is turned off whenever tryptophan is added to the growth medium.Rate this question:
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- 4.
This protein is produced by a regulatory gene
- A.
Operon
- B.
Inducer
- C.
Promotor
- D.
Repressor
- E.
Corepressor
Correct Answer
D. RepressorExplanation
A repressor is a protein that is produced by a regulatory gene and is responsible for inhibiting the expression of genes. It binds to the operator region of the DNA, preventing the RNA polymerase from transcribing the genes downstream. This allows the repressor to control the expression of genes by blocking their transcription. Therefore, the given statement suggests that the protein produced by the regulatory gene is a repressor.Rate this question:
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- 5.
A mutation in this section of DNA could influence the binding of RNA polymerase to the DNA
- A.
Operon
- B.
Inducer
- C.
Promoter
- D.
Repressor
- E.
Corepressor
Correct Answer
C. PromoterExplanation
A mutation in the promoter region of DNA could affect the binding of RNA polymerase to the DNA. The promoter is a specific sequence of DNA that acts as a binding site for RNA polymerase, which is an enzyme responsible for initiating transcription. If there is a mutation in the promoter region, it could alter the sequence and disrupt the binding of RNA polymerase, leading to a decrease or loss of transcription of the gene or genes regulated by that promoter.Rate this question:
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- 6.
A lack of this nonprotein molecule would result in the inability of the cell to "turn off" genes
- A.
Operon
- B.
Inducer
- C.
Promoter
- D.
Repressor
- E.
Corepressor
Correct Answer
E. CorepressorExplanation
A lack of corepressor would result in the inability of the cell to "turn off" genes. Corepressors are small molecules that bind to repressor proteins and enable them to bind to DNA, preventing the transcription of specific genes. Without corepressors, repressor proteins would not be able to effectively bind to DNA and inhibit gene expression, leading to the inability of the cell to "turn off" genes.Rate this question:
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- 7.
When this is taken up by the cell, it binds to the repressor so that the repressor no longer binds to the operator
- A.
Operon
- B.
Inducer
- C.
Promoter
- D.
Repressor
- E.
Corepressor
Correct Answer
B. InducerExplanation
The inducer is a molecule that, when taken up by the cell, binds to the repressor protein. This binding prevents the repressor from binding to the operator, which is a DNA sequence that controls the expression of genes in an operon. By binding to the repressor, the inducer allows the RNA polymerase to access the promoter region and initiate gene transcription. Therefore, the presence of the inducer molecule leads to the activation of gene expression in the operon.Rate this question:
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- 8.
For a repressible operon to be transcribed, which of the following must occur?
- A.
A corepressor must be present
- B.
RNA polymerase and the active repressor must be present
- C.
RNA polymerase must bind to the promoter, and the respressor must be inactive
- D.
RNA polymerase cannot be present, and the repressor must be inactive
- E.
RNA polymerase must not occupy the promoter, and the repressor must be inactive
Correct Answer
C. RNA polymerase must bind to the promoter, and the respressor must be inactiveExplanation
In order for a repressible operon to be transcribed, RNA polymerase must bind to the promoter, which is the region of DNA where transcription begins. Additionally, the repressor protein, which normally binds to the operator region of the operon to prevent transcription, must be inactive. This allows RNA polymerase to proceed with transcription and produce the necessary mRNA.Rate this question:
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- 9.
If glucose is available in the environment of E.coli, the cell responds with very low concentration of cAMP. When the cAMP increases in concentration, it binds to CAP. Which of the following would you expect would then be a measurable effect?
- A.
Decreased concentration of the lac enzymes
- B.
Increased concentration of the trp enzymes
- C.
Decreased binding of the RNA polymerase to sugar metabolism - related promoters
- D.
Decreased concentration of alternative sugars in the cell
- E.
Increased concentration of sugars such as arabinose in the cell
Correct Answer
E. Increased concentration of sugars such as arabinose in the cellExplanation
When glucose is available in the environment of E.coli, the cell responds by producing a low concentration of cAMP. However, when cAMP levels increase, it binds to CAP (catabolite activator protein), which leads to the activation of certain genes involved in sugar metabolism. This activation would result in an increased concentration of sugars, such as arabinose, in the cell. Therefore, the measurable effect would be an increased concentration of sugars like arabinose in the cell.Rate this question:
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- 10.
Two potential devices that eukaryotic cells use to regulate transcription are
- A.
DNA methylation and histone amplification
- B.
DNA amplification and histone methylation
- C.
DNA acetylation and methylation
- D.
DNA methylation and histone acetylation
- E.
Histone amplification and DNA acetylation
Correct Answer
D. DNA methylation and histone acetylationExplanation
Eukaryotic cells regulate transcription through various mechanisms, including DNA methylation and histone acetylation. DNA methylation involves the addition of a methyl group to the DNA molecule, which can lead to gene silencing and decreased transcription. Histone acetylation, on the other hand, involves the addition of an acetyl group to histone proteins, which relaxes the chromatin structure and allows for increased transcription. Therefore, DNA methylation and histone acetylation are two potential devices that eukaryotic cells use to regulate transcription.Rate this question:
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- 11.
This binds to a site in the DNA far from the promoter to stimulate transcription
- A.
Enhancer
- B.
Promoter
- C.
Activator
- D.
Repressor
- E.
Terminator
Correct Answer
C. ActivatorExplanation
An activator is a protein that binds to a specific site in the DNA, known as an enhancer, which is located far from the promoter region. This binding event stimulates the transcription process, leading to increased gene expression. Unlike a repressor, which inhibits transcription, an activator enhances or activates gene expression. Therefore, an activator is the most suitable option to explain the given statement.Rate this question:
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- 12.
This can inhibit transcription by blocking the binding of positively acting transcription factors to the DNA
- A.
Enhancer
- B.
Promoter
- C.
Activaor
- D.
Repressor
- E.
Terminator
Correct Answer
D. RepressorExplanation
A repressor can inhibit transcription by binding to the DNA and preventing the binding of positively acting transcription factors. This binding prevents the formation of the transcription initiation complex and blocks the RNA polymerase from starting transcription. Therefore, the presence of a repressor can effectively shut down gene expression by inhibiting transcription.Rate this question:
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- 13.
This is the site in the DNA located near the end of the final exon, encoding an RNA sequence that determines the 3' end of the transcript
- A.
Enhancer
- B.
Promoter
- C.
Activator
- D.
Repressor
- E.
Terminator
Correct Answer
E. TerminatorExplanation
The correct answer is terminator. The terminator is a site in the DNA that is located near the end of the final exon. It encodes an RNA sequence that determines the 3' end of the transcript. The terminator is responsible for signaling the end of transcription and helps in the termination of RNA synthesis.Rate this question:
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- 14.
A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments using this procedure in Drosophila, she was readily successful in increasing phosphorylation of amino acids adjacent to methylated amino acids in histone tails. Which of the following results would she most likely see?
- A.
Increased chromatin condensation
- B.
Decreased chromatin concentration
- C.
Abnormalities of mouse embryos
- D.
Decreased binding of transcription factors
- E.
Inactivation of the selected genes
Correct Answer
B. Decreased chromatin concentrationExplanation
If the researcher is successful in increasing phosphorylation of amino acids adjacent to methylated amino acids in histone tails, it is likely that this modification will lead to decreased chromatin concentration. Phosphorylation and methylation are known to affect the structure and packaging of chromatin, with phosphorylation generally associated with more relaxed chromatin and methylation associated with more condensed chromatin. Therefore, increasing phosphorylation in this context would likely result in a decrease in chromatin concentration.Rate this question:
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- 15.
A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. In one set of experiments she succeeded in decreasing methylation of histone tails. Which of the following results would she most likely see?
- A.
Increased chromatin condensation
- B.
Decreased chromatin concentration
- C.
Abnormalities of mouse embryos
- D.
Decreased binding of transcription factors
- E.
Inactivation of the selected genes
Correct Answer
A. Increased chromatin condensationExplanation
When the researcher decreases methylation of histone tails, it is likely to result in increased chromatin condensation. Methylation of histone tails is associated with a more open chromatin structure, allowing for gene expression. When methylation is decreased, the chromatin becomes more condensed, leading to a tighter packing of DNA and potentially inhibiting gene expression. Therefore, the most likely result of decreasing methylation of histone tails would be increased chromatin condensation.Rate this question:
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- 16.
A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. One of her colleagues suggested she try increased methylation of C nucleotides in a mammalian system. Which of the following results would she most likely see?
- A.
Increased chromatin condensation
- B.
Decreased chromatin concentration
- C.
Abnormalities of mouse embryos
- D.
Decreased binding of transcription factors
- E.
Inactivation of the selected genes
Correct Answer
E. Inactivation of the selected genesExplanation
If the researcher increases methylation of C nucleotides in a mammalian system, she would most likely see the inactivation of the selected genes. Methylation of DNA can lead to gene silencing or inactivation, as it prevents the binding of transcription factors and other proteins necessary for gene expression. This can result in the selected genes being turned off or not functioning properly.Rate this question:
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- 17.
A researcher found a method she could use to manipulate and quantify phosphorylation and methylation in embryonic cells in culture. She tried decreasing the amount of methylation enzymes in the embryonic stem cells and then allowed the cells to further differentiate. Which of the following results would she most likely see?
- A.
Increased chromatin condensation
- B.
Decreased chromatin concentration
- C.
Abnormalities of mouse embryos
- D.
Decreased binding of transcription factors
- E.
Inactivation of the selected genes
Correct Answer
C. Abnormalities of mouse embryosExplanation
By decreasing the amount of methylation enzymes in the embryonic stem cells, the researcher is likely to disrupt the normal process of DNA methylation, which plays a crucial role in embryonic development. Methylation is involved in regulating gene expression and maintaining the stability of the genome. Therefore, a decrease in methylation enzymes could lead to abnormalities in mouse embryos as the normal development process is disrupted.Rate this question:
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- 18.
Gene expression might be altered at the level of post-transcriptional processing in eukaryotes rather than prokaryotes because of which of the following?
- A.
Eukaryotic mRNAs get 5ʹ caps and 3ʹ tails.
- B.
Prokaryotic genes are expressed as mRNA, which is more stable in the cell.
- C.
Eukaryotic exons may be spliced in alternative patterns.
- D.
Prokaryotes use ribosomes of different structure and size.
- E.
Eukaryotic coded polypeptides often require cleaving of signal sequences before localization.
Correct Answer
C. Eukaryotic exons may be spliced in alternative patterns.Explanation
Eukaryotic exons may be spliced in alternative patterns, which means that different combinations of exons can be joined together to form mature mRNA. This alternative splicing allows for the production of multiple protein isoforms from a single gene, increasing the complexity and diversity of gene expression in eukaryotes. In contrast, prokaryotes do not undergo alternative splicing and their genes are generally expressed as a single continuous mRNA sequence. Therefore, post-transcriptional processing, such as alternative splicing, is more likely to alter gene expression in eukaryotes rather than prokaryotes.Rate this question:
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- 19.
Which of the following statements describes proto-oncogenes?
- A.
They are introduced to a cell initially by retroviruses.
- B.
They are produced by somatic mutations induced by carcinogenic substances
- C.
Their normal function is to suppress tumor growth
- D.
They can code for proteins associated with cell growth.
- E.
They are underexpressed in cancer cells
Correct Answer
D. They can code for proteins associated with cell growth.Explanation
Proto-oncogenes are genes that have the potential to become oncogenes, which are genes that can cause cancer. They are not introduced to a cell by retroviruses or produced by somatic mutations induced by carcinogenic substances. Their normal function is not to suppress tumor growth, but rather to regulate normal cell growth and division. Proto-oncogenes can code for proteins that are involved in cell growth, and when mutated or overexpressed, they can lead to uncontrolled cell growth and the development of cancer. They are not underexpressed in cancer cells, as their abnormal activation is often associated with cancer development.Rate this question:
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- 20.
Which of the following is characteristic of the product of the p53 gene?
- A.
It speeds up the cell cycle
- B.
It causes cell death via apoptosis
- C.
It is an activator for other genes
- D.
It allows cells to pass on mutations due to DNA damage
- E.
It slows down the rate of DNA replication by interfering with the binding of DNA polymerase
Correct Answer
C. It is an activator for other genesExplanation
The product of the p53 gene is an activator for other genes. This means that it plays a role in regulating the expression of other genes in the cell. It can bind to specific DNA sequences and activate the transcription of target genes, which can then lead to various cellular responses such as DNA repair, cell cycle arrest, or apoptosis. By acting as an activator for other genes, the p53 gene product helps maintain the integrity of the genome and regulate cell growth and division.Rate this question:
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- 21.
Altering patterns of gene expression in prokaryotes would most likely serve the organismʹs survival in which of the following ways?
- A.
Organizing gene expression so that genes are expressed in a given order
- B.
Allowing each gene to be expressed an equal number of times
- C.
Allowing environmental changes to alter the prokaryoteʹs genome
- D.
Allowing the organism to adjust to changes in environmental conditions
- E.
Allowing young organisms to respond differently from more mature org
Correct Answer
D. Allowing the organism to adjust to changes in environmental conditionsExplanation
Altering patterns of gene expression in prokaryotes allows the organism to adjust to changes in environmental conditions. This is because prokaryotes can regulate which genes are expressed and when, allowing them to respond to different environmental cues. By adjusting gene expression, prokaryotes can produce the necessary proteins and enzymes to adapt to changes in temperature, nutrient availability, or other environmental factors. This flexibility in gene expression enables prokaryotes to survive and thrive in various conditions and increase their chances of survival.Rate this question:
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- 22.
In response to chemical signals, prokaryotes can do which of the following?
- A.
Turn off translation of their mRNA
- B.
Alter the level of production of various enzymes
- C.
Increase the number and responsiveness of their ribosomes
- D.
Inactivate their mRNA molecules
- E.
Alter the sequence of amino acids in certain proteins
Correct Answer
B. Alter the level of production of various enzymesExplanation
Prokaryotes can alter the level of production of various enzymes in response to chemical signals. This means that they can regulate the amount of enzymes they produce based on the signals they receive. This allows them to adapt and respond to changes in their environment, ensuring that they have the necessary enzymes for specific metabolic processes. By adjusting enzyme production, prokaryotes can optimize their cellular functions and survive in different conditions.Rate this question:
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- 23.
Steroid hormones produce their effects in cells by
- A.
Activating key enzymes in metabolic pathways
- B.
Activating translation of certain mRNAs
- C.
Promoting the degradation of specific mRNAs
- D.
Promoting the formation of looped domains in certain regions of DNA.
- E.
Binding to intracellular receptors and promoting transcription of specific genes
Correct Answer
E. Binding to intracellular receptors and promoting transcription of specific genesExplanation
Steroid hormones are able to produce their effects in cells by binding to intracellular receptors and promoting the transcription of specific genes. This binding activates the receptors, which then act as transcription factors to bind to specific regions of DNA and initiate the process of gene transcription. This leads to the production of specific proteins that mediate the hormone's effects on the target cells.Rate this question:
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- 24.
Forms of the ras protein found in tumors usually cause which of the following?
- A.
Cell-to-cell adhesion to be nonfunctional
- B.
Growth factor signaling to be hyperactive
- C.
DNA replication to stop
- D.
DNA replication to be hyperactive
- E.
Cell division to cease
Correct Answer
B. Growth factor signaling to be hyperactiveExplanation
The ras protein is a key regulator of cell growth and division. When forms of the ras protein are found in tumors, they often have mutations that cause the protein to be hyperactive. This means that the signaling pathways for growth factors, which normally control cell growth and division, become overactive. As a result, the cells in the tumor can grow and divide uncontrollably, leading to the development and progression of the tumor.Rate this question:
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