Question 1

Which of the following is true about the holoenzyme in an open complex?

Accepted Answer

In the open complex, the DNA is primarily bound to the sigma subunit, which helps in recognizing the promoter regions.

Question 2

______________ can be used to block initiation of RNA synthesis.

Accepted Answer

Rifampicin

Question 3

The sigma subunit in RNA polymerase is necessary for the transcription of intermediate genes and RNA elongation.

Accepted Answer

The sigma subunit in RNA polymerase is primarily responsible for promoter recognition and initiation of transcription, not for the transcription of intermediate genes or RNA elongation.

Question 4

An experiment was conducted to determine the hairpin loop region in termination.Two DNA templates were prepared and used in an in vitro transcription assay.The samples were analyzed for release of the RNA polymerase.Construct 1 - hairpin sequence removed; Construct 2 - two copies of hairpin sequence inserted; Construct 3 - normal DNA with only one hairpin sequence  The data from this experiment suggest that

Accepted Answer

The answer of An experiment was conducted to determine the...

Question 5

Which of the following are characteristic of intrinsic terminator elements?

Accepted Answer

Intrinsic terminators in bacteria typically have a region forming a hairpin loop due to an inverted repeat, followed by a string of adenines in the template strand, which corresponds to several thymine (T) bases in the nontemplate strand of DNA. This structure facilitates the termination of transcription.

Question 6

Which of the following would most likely occur if an in vitro transcription assay is performed using a cell extract containing an alpha subunit without the C-terminal domain?

Accepted Answer

The C-terminal domain of the alpha subunit is responsible for interaction with regulatory proteins and is important for promoter recognition and transcription initiation. Without the C-terminal domain, the polymerase complex would be loosely associated with the promoter, decreasing the efficiency of transcription initiation. Therefore, choice D is the best choice. Choices A, B, C, and E are unlikely to occur.

Question 7

Which of the following statement is false regarding the sigma-factor?

Accepted Answer

Sigma factors do have a DNA-binding domain, which is crucial for their role in recognizing specific promoter regions on the DNA to initiate transcription.

Question 8

Dimethyl sulfate is used to

Accepted Answer

Dimethyl sulfate is a mutagenic agent that adds a methyl group to DNA. It can modify the nitrogenous bases of DNA, leading to base-pair mismatches and mutations.

Question 9

Which of the following precursors would be most appropriate to use in an experiment of the first 10 nucleotides in the initiation phase of transcription?

Accepted Answer

The correct precursor for studying the initiation phase of transcription, especially the first 10 nucleotides, would need to be a molecule that can be incorporated into the nascent RNA chain. Option A, with its ATP designation, suggests it is an adenosine triphosphate variant, which is a nucleotide used in RNA synthesis. The complex notation likely indicates modifications to standard ATP to track or influence the initiation phase of transcription, making it the most appropriate choice for such an experiment.

Question 10

Which of the following is most involved in elongation of the RNA transcript?

Accepted Answer

Sigma factor is primarily involved in the initiation phase of transcription in bacteria, helping the RNA polymerase to bind to the promoter. However, the question asks about elongation, and none of the options directly relate to the elongation phase of RNA transcription. Therefore, it seems there might be a misunderstanding in the question or options provided. Typically, the RNA polymerase core enzyme is responsible for the elongation of the RNA transcript after the sigma factor has facilitated the initiation phase.

Question 11

An experiment was designed to obtain nonspecific transcription from both strands of a DNA molecule.Which of the following strategies would be most effective in achieving this?

Accepted Answer

The core enzyme of RNA polymerase can transcribe DNA nonspecifically, as it lacks the sigma factor, which is responsible for promoter-specific transcription initiation.

Question 12

Which of the following techniques is suitable for the study of DNA:RNA hybrid formation during transcription?

Accepted Answer

DNA:RNA crosslinking is the most suitable technique for studying DNA:RNA hybrid formation during transcription. This technique involves the use of psoralen or UV light to covalently crosslink mRNA to the DNA template before isolation and analysis. This allows for the detection and identification of specific DNA:RNA hybrids, giving insight into the mechanism of transcription.

Question 13

Which of the following compounds is effective in inhibiting RNA chain polymerization in an in vitro transcription assay?

Accepted Answer

The answer of Which of the following compounds is effective...

Question 14

Which of the following is not present in the core RNA polymerase?

Accepted Answer

The answer of Which of the following is not present...

Question 15

The DNA binding sites for RNA polymerases are called ______________.

Accepted Answer

The answer of The DNA binding sites for RNA polymerases...

Question 16

Place the following in the order that they occur during transcription initiation: 1 - formation of open complex; 2 - formation of closed complex;
3 promoter clearance; 4 - synthesis of about 10 nucleotides

Accepted Answer

The correct order for transcription initiation is: formation of a closed complex, formation of an open complex, synthesis of about 10 nucleotides, and then promoter clearance. However, there seems to be a typographical error in the choices provided. The logical sequence based on the process described should be 2 (formation of closed complex), 1 (formation of open complex), 4 (synthesis of about 10 nucleotides), and then 3 (promoter clearance). The correct sequence isn't listed as provided, indicating a mistake in the question's options. The intended correct sequence likely aimed to be 2,1,4,3, but due to a typographical error, choice B is the closest match despite its repetition and error.

Question 17

Which of the following does not have a DNA-binding domain?

Accepted Answer

The UP region does not have a DNA-binding domain; it is a sequence in the promoter region of genes that enhances the binding of RNA polymerase to DNA. Sigma-factor, alpha-factor, beta, and beta prime are all components or factors associated with RNA polymerase or transcription regulation that interact with DNA or RNA in various ways.

Question 18

Which of the following techniques would be most useful in testing the ability of the core RNA polymerase to bind to the promoter?

Accepted Answer

DNAse footprinting is a technique that can be used to identify the specific DNA sequence that is bound by a protein. In this case, the core RNA polymerase can be incubated with a segment of DNA that includes the promoter region, and then treated with DNAse to cut the DNA at unprotected regions. The resulting fragments can be separated by gel electrophoresis and compared to a control sample without the RNA polymerase, allowing for identification of the protected region where the RNA polymerase is bound. This technique would thus be most useful in testing the ability of the core RNA polymerase to bind to the promoter.

Question 19

Which of the following is incorrect regarding rho-dependent terminators?

Accepted Answer

Rho does not have helicase activity.

Question 20

Which of the following factors is involved in proofreading during transcription?

Accepted Answer

GreB is involved in transcription proofreading by stimulating RNA polymerase to cleave the nascent RNA, allowing correction of errors.

Quiz 6: The Mechanism of Transcription in Bacteria