Deck 6: The Mechanism of Transcription in Bacteria

Question 1

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

A)The DNA is bound mainly to the sigma-subunit.
B)There no interaction between the sigma factor and the -10 region.
C)There are two Na⁺ ions in the core enzyme .
D)Region 2.4 of the sigma-factor binds to the -35 region.
E)The DNA is bound mainly to the sigma-subunit and there no interaction between the sigma factor and the -10 region are both true.

Answer 1

A

Question 2

______________ can be used to block initiation of RNA synthesis.

Answer 2

Rifampicin

Question 3

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

Answer 3

False

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

A)hairpin loops are not required for termination.
B)two hairpin loops rapidly destabilize the polymerase.
C)the data are inconclusive.
D)additional hairpin loops increase the stability of the RNA:DNA hybrid.
E)both hairpin loops are not required for termination and two hairpin loops rapidly destabilize the polymerase are possible explanations.

Question 5

Which of the following are characteristic of intrinsic terminator elements?

A)They contain an inverted repeat.
B)They contain a hairpin loop.
C)They contain several T's in the nontemplate strand of DNA.
D)Only They contain an inverted repeat and they contain a hairpin loop are correct.
E)They contain an inverted repeat,they contain a hairpin loop,and they contain several T's in the nontemplate strand of DNA are correct.

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?

A)Polymerase would become tightly associated with the promoter.
B)Polymerase would become more susceptible to proteolysis.
C)Transcription will be accelerated.
D)Polymerase complex would be loosely associated with the promoter.
E)Recognition of the UP element would be faster.

Question 7

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

A)It does not have a DNA-binding domain.
B)Interaction with the core enzyme unmasks the DNA-binding region.
C)Subregions 2.4 and 4.4 are involved in promoter recognition.
D)It can also bind to the nontemplate strand.
E)It can bind to the -10 box.

Question 8

Dimethyl sulfate is used to

A)cleave DNA molecules.
B)denature or melt DNA promote region.
C)remove methyl groups from RNA.
D)add methyl groups to DNA.
E)promote the binding of RNA polymerase to DNA.

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?

A)[ $\alpha$ -³²P]ATP
B)[¹⁴-C]dATP
C)[ $\beta$ -³²P]ATP
D)[ $\gamma$ -³²P]ATP
E)[¹⁴C]CTP

Question 10

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

A)sigma factor
B)UP elements
C)-10 region
D)both sigma factor and UP elements

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?

A)Include the RNA holoenzyme in the reaction.
B)Use the core enzyme of RNA polymerase.
C)Enrich the preparation with sigma subunit.
D)Use intact DNA .
E)Include the RNA holoenzyme in the reaction and use the core enzyme of RNA polymerase are both effective.

Question 12

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

A)DNA:protein crosslinking
B)DNAase I footprinting
C)DNA:RNA crosslinking
D)two-dimensional PAGE
E)FRET analysis

Question 13

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

A)treptomycin
B)ampicillin
C)streptolydigin
D)treptomycin and ampicillin
E)ampicillin and streptolydigin

Question 14

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

A) $\beta$
B) $\beta$ F'
C) $\sigma$
D)both $\beta$ and $\sigma$
E)none of the choices are correct.

Question 15

The DNA binding sites for RNA polymerases are called ______________.

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

A)1,2,3,4
B)2,1,4,2
C)2,1,2,4
D)3,1,2,4
E)3,2,1,4

Question 17

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

A)sigma-factor
B)UP region
C)alpha-factor
D)beta
E)beta prime

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?

A)gel filtration
B)S1 mapping
C)immunoblotting
D)DNAse footprinting
E)northern blotting

Question 19

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

A)They contain several T's in the notemplate strand.
B)They consist of inverted repeats.
C)They form hairpin loops.
D)Rho binds to the growing transcripts.
E)Rho has helicase activity.

Question 20

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

A)GreB
B)NusA
C)sigma-factor
D)rho-factor
E)none of the choices are correct.

Question 21

TATAAT is a consensus sequence located at -10 upstream of the transcription start site.

Question 22

The alpha subunit recognizes the UP promoter element.

Question 23

The core RNA polymerase must bind tightly to the promoter in order to initiate transcription.

Question 24

The catalytic centers of some polymerase cores contain magnesium ions.

Question 25

As transcription proceeds,the strain introduced in DNA is relaxed by DNA topoisomerases.

Question 26

The FRET technique allows the study of the movement of two molecules relative to each other.

Question 27

A closed promoter complex is one in which the holoenzyme is loosely bound and the DNA remains in double-stranded form.