Transcription: Copying DNA to RNA

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Questions and Answers

Which of the following scenarios would most likely result in a complete blockage of transcription in a eukaryotic cell?

The addition of acetyl groups to histone proteins near the promoter region of a gene.
A mutation in a silencer region that prevents the binding of a repressor protein.
The presence of a non-functional TFIID complex that cannot bind to the TATA box. (correct)
A slight decrease in the concentration of available CTP and GTP nucleotides.

If a eukaryotic cell's RNA Polymerase II was unable to be phosphorylated, what would be the most likely consequence?

The cell would stall during the elongation phase due to the polymerase's inability to maintain a stable transcription bubble.
The cell would fail to terminate transcription properly due to deficient signaling.
The cell would be unable to initiate transcription because the PIC could not form.
The cell would initiate transcription, but RNA Pol II would remain bound to the promoter, preventing further transcription cycles. (correct)

Consider a bacterial cell where a mutation has occurred, preventing the Rho factor from functioning correctly. Which outcome is most likely?

Transcription initiation will be blocked due to the sigma factor's inability to recognize promoter regions.
Transcription will continue indefinitely, producing abnormally long RNA molecules.
Transcription will proceed normally, as Rho factor is only a backup termination mechanism.
Termination of transcription will only occur at intrinsic termination sites. (correct)

A researcher is studying a newly discovered eukaryotic gene and observes that its transcription rate is significantly reduced after exposure to a specific chemical. Further analysis reveals that the chemical does not directly interact with the DNA or any transcription factors. What is the most probable mechanism by which this chemical is affecting transcription?

The chemical is inducing hypercondensation of chromatin in the region surrounding the gene. (B) Signup and view all the answers

In a hypothetical scenario, a mutation in a eukaryotic cell results in a non-functional TFIIH. What is the most direct consequence of this mutation on transcription?

The DNA double helix will be unable to unwind at the transcription start site. (C) Signup and view all the answers

Which of the following scenarios would have the most significant impact on the ability of a eukaryotic cell to produce a specific protein?

A mutation in the gene encoding for an snRNA required for splicing. (A) Signup and view all the answers

A scientist introduces a mutation into the gene for the sigma factor in bacteria. Which of the following outcomes would you predict?

Transcription would initiate at random sites along the DNA. (C) Signup and view all the answers

A researcher discovers a new molecule that inhibits the function of the spliceosome. What direct effect would this molecule have on gene expression in eukaryotes?

Production of pre-mRNA molecules with unspliced introns. (C) Signup and view all the answers

If a mutation occurred in the gene encoding the AAUAAA sequence in eukaryotes, what would be the most likely consequence?

The transcript would not be cleaved and polyadenylated correctly. (D) Signup and view all the answers

Which of the following scenarios would be most likely to result in the constitutive (always on) expression of a gene that is normally tightly regulated?

A mutation that prevents the binding of a repressor to a silencer. (C) Signup and view all the answers

What is the most direct consequence of treating eukaryotic cells with a drug that inhibits the enzyme responsible for adding the 7-methylguanosine cap to mRNA?

Decreased stability of mRNA and impaired translation initiation. (A) Signup and view all the answers

A mutation occurs in a bacterium that prevents the formation of the hairpin loop structure during intrinsic transcription termination. What is the most likely outcome?

Transcription will continue past the termination site, producing longer transcripts. (D) Signup and view all the answers

Which of the following scenarios would most directly lead to a decrease in gene expression due to transcriptional gene silencing (TGS)?

Recruitment of a microRNA complex to the DNA, inducing methylation. (D) Signup and view all the answers

How does the action of α-amanitin, a toxin found in poisonous mushrooms, directly interfere with eukaryotic gene expression?

It inhibits the activity of RNA Polymerase II, blocking mRNA synthesis. (B) Signup and view all the answers

What is the primary mechanism by which DNA methylation typically leads to transcriptional repression in eukaryotes?

By recruiting proteins that compact chromatin and inhibit transcription. (D) Signup and view all the answers

How would a significant deficiency in the availability of ATP, UTP, CTP and GTP most directly impact the process of transcription?

Slowing down the synthesis of the RNA molecule. (D) Signup and view all the answers

A researcher discovers that a particular gene is transcribed at a much lower rate in differentiated cells compared to embryonic stem cells. Which of the following epigenetic mechanisms is most likely responsible for this difference?

Increased acetylation of histones in the embryonic stem cells. (C) Signup and view all the answers

A eukaryotic cell is treated with a drug that inhibits the addition of the poly(A) tail to mRNA molecules. What is the most likely consequence of this treatment?

Decreased mRNA stability and reduced translation efficiency. (D) Signup and view all the answers

Which of the following best describes how a mutation in a gene coding for a transcription factor could affect transcription?

It could result in a non-functional transcription factor, altering gene expression. (D) Signup and view all the answers

A researcher is studying a bacterial gene and identifies a mutation in the -35 sequence of the promoter. What effet, if any, would you expect this mutation to have?

RNA polymerase will not be able to recognize and bind to the promoter. (D) Signup and view all the answers

Flashcards

Transcription

Biological process where DNA's genetic information is copied into a complementary RNA molecule.

The role of RNA

Serves as intermediate for carrying instructions from DNA to ribosomes, facilitates protein synthesis.