Conserved Proteins Quiz
- 1.
Which of the following statements is FALSE?
- A.
Sequence-specific protein DNA interactions require contact with the bases of DNA.
- B.
Sequence-independent protein DNA interactions are mostly electrostatic in nature.
- C.
Most sequence-specific protein-DNA interactions involve major groove.
- D.
Promoters are recognized by siRNA.
- E.
Zinc finger domains from the mouse transcription factor Zif268 interact mostly with the major groove on its target DNA.
Correct Answer
D. Promoters are recognized by siRNA.Explanation
The statement that promoters are recognized by siRNA is false. Promoters are typically recognized by transcription factors, which are proteins that bind to specific DNA sequences to regulate gene expression. siRNA (small interfering RNA) is involved in post-transcriptional gene silencing and does not directly recognize promoters.Rate this question:
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- 2.
During which of the following processes are RNA-DNA hybrids observed?
- A.
Transcription, prokaryotic only.
- B.
Replication, prokaryotic only.
- C.
Replication, eukaryotic only.
- D.
Replication and transcription, both eukaryotic and prokaryotic.
- E.
Translation, both eukaryotic and prokaryotic.
Correct Answer
D. Replication and transcription, both eukaryotic and prokaryotic.Explanation
RNA-DNA hybrids are observed during both replication and transcription in both eukaryotic and prokaryotic organisms. In replication, RNA primers are used to initiate DNA synthesis, resulting in RNA-DNA hybrids. In transcription, RNA molecules are synthesized using DNA as a template, forming RNA-DNA hybrids. Therefore, the correct answer is that RNA-DNA hybrids are observed during both replication and transcription in both eukaryotic and prokaryotic organisms.Rate this question:
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- 3.
Choose the correct statement.
- A.
Eukaryotic rRNA genes are processed in the nucleolus.
- B.
Eukaryotic genes often contain regions that are transcribed and later excised from the RNA, called exons.
- C.
RNA catalysts are called repressors.
- D.
An AT-rich region found in eukaryotic promoters is called the AUG box.
- E.
Prokaryotic genetic units called introns typically contain genes with related functions.
Correct Answer
A. Eukaryotic rRNA genes are processed in the nucleolus.Explanation
Eukaryotic rRNA genes are processed in the nucleolus. The nucleolus is a specialized region within the nucleus where ribosomal RNA (rRNA) is transcribed, processed, and assembled into ribosomes. This process involves the removal of non-coding regions, called introns, from the primary rRNA transcript. After processing, the mature rRNA molecules are exported to the cytoplasm where they combine with proteins to form ribosomes. This statement accurately describes the location and process of rRNA gene processing in eukaryotic cells.Rate this question:
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- 4.
The expressed sequences of eukaryotic pre-mRNAs are known as ____.
- A.
Introns
- B.
Operons
- C.
Exons
- D.
Promoters
- E.
AUG box
Correct Answer
C. ExonsExplanation
Exons are the expressed sequences of eukaryotic pre-mRNAs. They are the coding regions of the gene that are transcribed into mRNA and eventually translated into protein. Introns, on the other hand, are non-coding regions that are removed during RNA splicing. Operons are found in prokaryotes and consist of multiple genes controlled by a single promoter. Promoters are DNA sequences that initiate transcription. AUG box is a sequence found in the mRNA that signals the start of translation.Rate this question:
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- 5.
Most ____ have well defined 3'ends terminating in poly(A) tails of ~250 nucleotides.
- A.
Prokaryotic mRNAs
- B.
Prokaryotic rRNAs
- C.
Eukaryotic tRNAs
- D.
Eukaryotic mRNAs
- E.
Eukaryotic rRNAs
Correct Answer
D. Eukaryotic mRNAsExplanation
Eukaryotic mRNAs have well-defined 3' ends terminating in poly(A) tails of approximately 250 nucleotides. This poly(A) tail plays a crucial role in mRNA stability, transport, and translation. It helps protect the mRNA from degradation and allows it to be recognized and bound by specific proteins involved in various cellular processes. In contrast, prokaryotic mRNAs do not typically possess poly(A) tails and have different mechanisms for regulating mRNA stability and translation.Rate this question:
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- 6.
Which of the following statements best describes the role of sigma factors in bacterial gene expression?
- A.
Sigma factors determine which RNA polymerase is used during transcription.
- B.
Sigma factors mediate the excision of intronic sequences.
- C.
A cell's complement of sigma factors determines which of its genes are transcribed.
- D.
Sigma factors bind to the TATA box and initiate transcription.
- E.
None of the rest.
Correct Answer
C. A cell's complement of sigma factors determines which of its genes are transcribed.Explanation
Sigma factors are proteins that bind to RNA polymerase and direct it to specific promoters on the DNA molecule. These promoters contain consensus sequences, such as the TATA box, that are recognized by sigma factors. By binding to different sigma factors, RNA polymerase can recognize different promoters and initiate transcription of specific genes. Therefore, a cell's complement of sigma factors determines which of its genes are transcribed.Rate this question:
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- 7.
In eukaryotes, the three RNA polymerases recognize
- A.
A promoter sequence known as sigma factor.
- B.
A single promoter sequence.
- C.
A promoter sequence known as the Rho factor.
- D.
Different types of promoters.
- E.
None of the rest.
Correct Answer
D. Different types of promoters.Explanation
Eukaryote RNA polymerase recognize the different promoters with the help of transcription factors.
Option E was also accepted.Rate this question:
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- 8.
How does the preinitiation complex begin to form at a TATA box-containing eukaryotic promoter?
- A.
RNAP binds to the sigma factor.
- B.
RNAP binds to the initiator (Inr) element.
- C.
TATA-binding protein binds to the TATA box.
- D.
RNAP binds to the Rho factor.
- E.
None of the rest.
Correct Answer
C. TATA-binding protein binds to the TATA box.Explanation
The preinitiation complex begins to form at a TATA box-containing eukaryotic promoter when the TATA-binding protein binds to the TATA box. This binding event is crucial for the recruitment of other transcription factors and RNA polymerase to the promoter region, leading to the initiation of transcription. The TATA box serves as a recognition site for the TATA-binding protein, which then helps to position the RNA polymerase at the correct location on the DNA template for transcription to begin.Rate this question:
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- 9.
In eukaryotics, mRNAs are synthesized in the cell ____, whereas most translation occurs in the ____.
- A.
Cytosol, nucleosome.
- B.
Cytosol, nucleus.
- C.
Nucleosome, cytosol.
- D.
Nucleus, nucleosome.
- E.
Nucleus, cytosol.
Correct Answer
E. Nucleus, cytosol.Explanation
In eukaryotic cells, mRNAs are synthesized in the nucleus through a process called transcription. The DNA is transcribed into pre-mRNA, which is then processed and modified to form mature mRNA. After mRNA synthesis, it is transported out of the nucleus into the cytosol, where most of the translation process occurs. Translation is the process of protein synthesis, where the mRNA is used as a template to assemble amino acids into a polypeptide chain. Therefore, the correct answer is nucleus, cytosol.Rate this question:
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- 10.
Which of the following factors mediate(s) splicing?
- A.
Promoters
- B.
TBP
- C.
SMURFs
- D.
SnRNAs
- E.
TAFs
Correct Answer
D. SnRNAsExplanation
snRNAs, or small nuclear ribonucleoproteins, are essential factors that mediate splicing. They form complexes with proteins to create spliceosomes, which are responsible for removing introns and joining exons during mRNA processing. These snRNAs recognize specific sequences at the splice sites and catalyze the splicing reaction. Promoters, TBP (TATA-binding protein), SMURFs, and TAFs (TBP-associated factors) are not directly involved in the splicing process.Rate this question:
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- 11.
The phosphorylation of the CTD of RNA polymerase II is important for which phase of transcription?
- A.
Initial binding of the promoter
- B.
Conversion from the pre-initiation (closed) complex to the initiation (open) complex
- C.
Progression from initiation to elongation
- D.
Termination of transcription
- E.
None of the rest.
Correct Answer
C. Progression from initiation to elongationExplanation
The phosphorylation of the CTD of RNA polymerase II is important for the progression from initiation to elongation phase of transcription. This phosphorylation event allows for the recruitment of factors that are necessary for the transition from the initiation complex to the elongation complex. It also facilitates the release of RNA polymerase II from the promoter and allows it to start transcribing the DNA template. Therefore, the phosphorylation of the CTD is crucial for the efficient and successful progression of transcription from initiation to elongation.Rate this question:
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- 12.
RNA interference is a mechanism of posttranscriptional RNA-dependent
- A.
Chromatin-remodeling
- B.
Histone methylation
- C.
Apoptosis
- D.
Gene silencing
- E.
Coactivation
Correct Answer
D. Gene silencingExplanation
RNA interference is a mechanism in which small RNA molecules, such as microRNAs, bind to and degrade or inhibit the translation of specific messenger RNA (mRNA) molecules. This process leads to gene silencing, where the expression of a particular gene is reduced or completely turned off. Therefore, the correct answer is gene silencing.Rate this question:
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- 13.
Which of the following best describes the functioning of the lac repressor protein?
- A.
In the presence of allolactose, the protein binds the operator inhibiting transcription.
- B.
In the absence of allolactose, the protein binds the operator inhibiting transcription.
- C.
In the presence of allolactose, the protein binds the operator enhancing transcription.
- D.
In the absence of allolactose, the protein binds the operator enhancing transcription.
- E.
None of the rest.
Correct Answer
B. In the absence of allolactose, the protein binds the operator inhibiting transcription.Explanation
In the absence of allolactose, the lac repressor protein binds to the operator, which is a DNA sequence near the lac operon. This binding prevents the transcription machinery from accessing the promoter region, thus inhibiting transcription of the genes involved in lactose metabolism. This mechanism ensures that the lac operon is not transcribed when lactose is not available as an energy source.Rate this question:
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- 14.
Transcriptionally active DNA in eukaryotes is contained in ____.
- A.
Euchromatin
- B.
Heterochromatin
- C.
Cytosol
- D.
Endoplasmic reticulum
- E.
Liposome
Correct Answer
A. EuchromatinExplanation
Euchromatin is the correct answer because it refers to the portion of DNA that is actively transcribed and involved in gene expression in eukaryotic cells. Euchromatin is less condensed and more accessible to transcription factors and RNA polymerase, allowing for gene expression. In contrast, heterochromatin is highly condensed and transcriptionally inactive. Cytosol, endoplasmic reticulum, and liposomes are not directly involved in containing transcriptionally active DNA in eukaryotes.Rate this question:
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- 15.
Eukaryotic promoter regions can contain canonical sequences, which mark the site of transcription initiation. One such sequence is the TATA box. Transcription in eukaryotes is mediated by the TATA box in the following way:
- A.
RNA polymerase uses its sigma factor to bind to the TATA box and initiate transcription.
- B.
DNA polymerase uses its alpha-2 factor to bind to the TATA box and recruits RNA polymerase to initiate transcription.
- C.
The TATA box is not found in eukaryotes and is found only in prokaryotic promoter regions.
- D.
The TATA-binding protein (TBP), a subunit of TFIIB binds the TATA box and aids in transcription initiation.
- E.
The TATA-binding protein (TBP), a subunit of TFIID binds the TATA box and aids in transcription initiation.
Correct Answer
E. The TATA-binding protein (TBP), a subunit of TFIID binds the TATA box and aids in transcription initiation.Explanation
The TATA-binding protein (TBP), a subunit of TFIID, binds the TATA box and aids in transcription initiation. This is because the TATA box is a canonical sequence found in eukaryotic promoter regions that marks the site of transcription initiation. TBP specifically recognizes and binds to the TATA box, which helps to recruit RNA polymerase and initiate transcription.Rate this question:
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- 16.
You are a researcher studying a genetic disease, which results in neurodegeneration through production of an aberrant protein. To understand the impact this protein has within the cell, you decide to perform an experiment to reduce its expression in cells grown in a tissue culture. To do this, you:
- A.
Use siRNA to target the mRNA transcript encoding the aberrant protein and stop its production.
- B.
Add Neomycin, an aminoglycoside antibiotic that functions by halting protein synthesis within a cell, to your culture.
- C.
Add lactose to your cells to change their metabolic profile by activating the lac operon.
- D.
Use an inhibitor of cellular DNA polymerase to halt cellular transcription.
- E.
You cannot reduce expression of a protein within a cell.
Correct Answer
A. Use siRNA to target the mRNA transcript encoding the aberrant protein and stop its production.Explanation
The correct answer is to use siRNA to target the mRNA transcript encoding the aberrant protein and stop its production. siRNA is a powerful tool used to specifically silence the expression of a target gene by degrading its mRNA. By targeting the mRNA transcript encoding the aberrant protein, siRNA can effectively reduce its expression within the cell. This approach allows for a direct and specific manipulation of the protein levels, providing valuable insights into its impact on cellular function. The other options mentioned, such as adding Neomycin, lactose, or an inhibitor of cellular DNA polymerase, do not directly target the mRNA transcript of the aberrant protein and would not be effective in reducing its expression.Rate this question:
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- 17.
Prokaryotic mRNA encodes ____.
- A.
A single protein because it is monocistronic.
- B.
A single protein because it is polycistronic.
- C.
Multiple proteins because it is monocistronic.
- D.
Multiple proteins because it is polycistronic.
- E.
DNA.
Correct Answer
D. Multiple proteins because it is polycistronic.Explanation
Prokaryotic mRNA encodes multiple proteins because it is polycistronic. In prokaryotes, a single mRNA molecule can contain multiple coding regions called cistrons, each encoding a different protein. This is possible due to the presence of Shine-Dalgarno sequences and ribosome binding sites within the mRNA molecule, which allow multiple ribosomes to simultaneously bind and initiate translation at different start codons along the mRNA. As a result, multiple proteins can be produced from a single mRNA transcript in prokaryotes.Rate this question:
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- 18.
Which of the following statements regarding eukaryotic transcription is TRUE?
- A.
It makes use of an RNA polymerase enzyme, which seeks out and binds promoters using its sigma factor.
- B.
It produces a polycistronic mRNA allowing transcription and proteins synthesis to occur simultaneously.
- C.
It is carried out in the cytosol by components of the RISC complex and the Dicer protein.
- D.
It involves transcription factors, which facilitate transcription through protein-DNA and protein-protein interactions.
- E.
It is coupled to translation.
Correct Answer
D. It involves transcription factors, which facilitate transcription through protein-DNA and protein-protein interactions.Explanation
Eukaryotic transcription involves transcription factors, which are proteins that bind to specific DNA sequences called promoters. These transcription factors facilitate transcription by interacting with the DNA and other proteins involved in the transcription process. This interaction helps to recruit the RNA polymerase enzyme to the promoter and initiate transcription. Therefore, the statement that "It involves transcription factors, which facilitate transcription through protein-DNA and protein-protein interactions" is true.Rate this question:
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- 19.
____ is a process essential to maturation of eukaryotic mRNA, and allows for production of multiple proteins from one gene.
- A.
Transcription
- B.
Splicing
- C.
Translation
- D.
Replication
- E.
Transpeptidation
Correct Answer
B. SplicingExplanation
Splicing is the correct answer because it is a process in which the non-coding regions (introns) are removed from the pre-mRNA molecule, and the coding regions (exons) are joined together to form the mature mRNA. This process allows for the production of multiple proteins from one gene, as different combinations of exons can be spliced together to generate different mRNA transcripts and subsequently different protein products.Rate this question:
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- 20.
RNA transcription is apparently carried out by immobile protein complexes that reel in the ____.
- A.
MRNA
- B.
TRNA
- C.
NcRNA
- D.
RNA
- E.
DNA
Correct Answer
E. DNAExplanation
RNA transcription is the process by which genetic information from DNA is copied into RNA. In this process, immobile protein complexes act as a machinery to reel in the DNA template and synthesize RNA molecules. Therefore, the correct answer is DNA, as it is the template from which RNA is transcribed.Rate this question:
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- 21.
Chromatin remodeling may precede transcription. Which of the following is NOT a way that transcriptionally inactive DNA maintains a condensed state?
- A.
Degree of DNA methylation
- B.
Presence of variant histones
- C.
Methylation of the promoters
- D.
Pattern of histone modification
- E.
The histone code
Correct Answer
C. Methylation of the promotersExplanation
Methylation of the promoters is not a way that transcriptionally inactive DNA maintains a condensed state. Methylation of the promoters can actually lead to gene silencing and inhibition of transcription. In contrast, chromatin remodeling can involve the presence of variant histones, changes in the pattern of histone modification, and the histone code, all of which can contribute to maintaining a condensed state of DNA and inhibiting transcription. Additionally, the degree of DNA methylation can also play a role in gene regulation, with highly methylated DNA often associated with transcriptional silencing.Rate this question:
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- 22.
Which of the following is NOT one of the six highly conserved proteins that initiate transcription in eukaryotes?
- A.
TFIIA
- B.
TFIIB
- C.
TFIID
- D.
TFIIG
- E.
TFIIF
Correct Answer
D. TFIIGExplanation
TFIIG is not one of the six highly conserved proteins that initiate transcription in eukaryotes. The other options, TFIIA, TFIIB, TFIID, TFIIF, and TFIIG, are all part of the transcription initiation complex and play crucial roles in the process. However, TFIIG is not a known protein involved in transcription initiation, making it the correct answer.Rate this question:
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- 23.
During transcription, the DNA strands separate, and RNA polymerase constructs an RNA molecule that forms a short hybrid helix with the ____.
- A.
DNA
- B.
RNA polymerase
- C.
MRNA
- D.
Template strand
- E.
NcRNA
Correct Answer
D. Template strandExplanation
During transcription, the DNA strands separate, and RNA polymerase constructs an RNA molecule that forms a short hybrid helix with the template strand. The template strand is the strand of DNA that is used as a template to synthesize the complementary RNA molecule. RNA polymerase recognizes and binds to a specific region on the template strand, and then moves along the strand, adding complementary RNA nucleotides to form the RNA molecule. Therefore, the template strand is the correct answer as it is the strand of DNA that is directly involved in the synthesis of RNA during transcription.Rate this question:
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- 24.
When an activator binds to the enhancer, a protein complex known as Mediator links the enhancer-bound activator to the transcription machinery poised at the ____.
- A.
Exon
- B.
Intron
- C.
Telomere
- D.
Promoter
- E.
RNA polymerase
Correct Answer
D. PromoterExplanation
When an activator binds to the enhancer, a protein complex known as Mediator links the enhancer-bound activator to the transcription machinery poised at the promoter. The promoter is a region of DNA that signals the start of a gene and is responsible for initiating transcription. The Mediator complex helps in facilitating the communication between the activator and the transcription machinery, allowing for the efficient initiation of gene expression.Rate this question:
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- 25.
The shift from initiation to elongation in eukaryotes involves structural changes in RNA polymerase, including ____ of its C-terminal domain
- A.
Acetylation
- B.
Methylation
- C.
Phosphorylation
- D.
Amidation
- E.
Formylation
Correct Answer
C. PhosphorylationExplanation
During the shift from initiation to elongation in eukaryotes, RNA polymerase undergoes structural changes, including phosphorylation of its C-terminal domain. Phosphorylation refers to the addition of a phosphate group to a molecule, which can regulate protein activity and function. In this case, phosphorylation of the C-terminal domain of RNA polymerase is necessary for the transition from initiation to elongation, indicating that this modification plays a crucial role in the regulation of transcription in eukaryotes.Rate this question:
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Mar 20, 2023Quiz Edited by
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Dec 11, 2012Quiz Created by
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