Of the following, which is best to describe how the three eukaryotic RNA polymer
ID: 58534 • Letter: O
Question
Of the following, which is best to describe how the three eukaryotic RNA polymerases differ from one each other?
They differ by their ability to work in concert with the sigma factor.
They have differential sensitivities to alpha-amanitin.
They differ by their subunit composition: Pol I has 2 alpha-like subunits whereas Pol II has 2 beta-like subunits and Pol III 2 omega-like subunits, instead.
They differ by their sub-cellular localization: Pol I is nucleolar, Pol II is nuclear and Pol III is cytoplasmic.
3 points
QUESTION 2
Many eukaryotic genes are divided into mosaics of exons and introns. When comparing a mRNA species with its cognate primary transcript from which it was derived, which of the following is true?
The introns are translated but not transcribed.
The introns are transcribed but not translated.
The introns are both transcribed and translated.
The introns are neither transcribed nor translated.
3 points
QUESTION 3
Which enzyme catalyzes transcription of the majority of protein-coding genes in a eukaryotic cell?
RNA Polymerase I
DNA Polymerase II
DNA Polymerase I
RNA Polymerase III
RNA Polymerase II
3 points
QUESTION 4
Which of the following statements accurately describes RNA polymerase III but not RNA polymerase II?
It transcribes tRNA.
It transcribes RNA molecules required for ribosomal function.
It localizes to the nucleoli.
It is regulated by a unique carboxy-terminal domain.
It is inhibited by -amanitin at concentrations in the nanomolar range.
3 points
QUESTION 5
The fidelity of RNA pol II refers to
the enzyme's ability to select the correct nucleotide to add to the growing RNA chain.
the enzyme's ability to initiate transcription without the need for a preexisting primer.
the enzyme's ability to identify the correct promoter from which to initiate transcription.
the enzyme's ability to proceed along the DNA while sequentially catalyzing the addition of new NTPs to the growing RNA chain, without detaching prematurely from the DNA.
3 points
QUESTION 6
Which of the following supports the hypothesis that RNA pol II is a highly conserved enzyme?
Human genes encoding 10 of the 12 subunits can substitute for their yeast counterparts.
It is a large and complex enzyme comprising 12 subunits and a molecular mass of more than 500 kDal.
The large subunits of yeast and human RNA Pol II are essential for survival.
RNA Pol II in humans has more subunits than the corresponding enzyme of bacteria.
3 points
QUESTION 7
Match the items from the list of features of Pol II with the letter indicating their position on the image of the three dimensional crystal structure of the enzyme. Note that not all items in the list are used.
A
B
C
D
E
Jaw
Bridge
Active site
Clamp
Funnel
Wall
Switches
Cleft
3 points
QUESTION 8
Determine if the following statements regarding transcription initiation by RNA polymerase II are True or False.
Transcription in initiation in eukaryotes is a complicated process involving the orchestrated sequential binding of many proteins.
Several general transcription factors including the TATA-binding protein bind specifically to the promoter.
These transcription factors allow the recruitment of RNA polymerase II, followed by binding of additional factors to produce the closed initiation complex.
The complex is converted into the open initiation complex by the helicase activity of one of these transcription factors.
Phosphorylation of the polymerase results in a conformational change converting the polymerase into its elongation mode.
False
True
3 points
QUESTION 9
Which one of the following statements about eukaryotic RNA polymerases is correct?
Only eukaryotic RNA polymerase I recognizes prokaryotic promoters.
Only eukaryotic RNA polymerase III recognizes prokaryotic promoters.
All three eukaryotic RNA polymerases recognize the same promoters as prokaryotic polymerases.
None of the eukaryotic RNA polymerases recognizes prokaryotic promoters.
Only eukaryotic RNA polymerase II recognizes prokaryotic promoters.
3 points
QUESTION 10
Indicate whether each of the following statements about eukaryotic cells is True or False.
They have three distinct RNA polymerases.
Their mRNAs are generally synthesized by RNA polymerase I.
RNA polymerase III synthesizes only rRNAs.
The tRNAs are synthesized by RNA polymerase II.
Eukaryotic RNA polymerases are homologous to each other and to bacterial RNA polymerases.
False
True
3 points
QUESTION 11
All of the following statements about the essential carboxy terminal domain (CTD) of RNA polymerase are true except
The CTD is critical for viability.
The CTD is present in RNA polymerase I, II, and III.
The CTD can become phosphorylated.
The CTD of mammals contains more than 50 repeats of a heptapeptide.
They differ by their ability to work in concert with the sigma factor.
They have differential sensitivities to alpha-amanitin.
They differ by their subunit composition: Pol I has 2 alpha-like subunits whereas Pol II has 2 beta-like subunits and Pol III 2 omega-like subunits, instead.
They differ by their sub-cellular localization: Pol I is nucleolar, Pol II is nuclear and Pol III is cytoplasmic.
Explanation / Answer
1. They differ in sensitivities to alpha amanitin Pol I is insensitive, Pol II is sensitive at 1ug/ml and Pol III is sensitive at 10ug/ml.
2. The answer is The introns are transcribed but not translated. The introns will be removed by editing after transcription.
3. RNA Polymerase II transcribes most of protein coding genes which are about 25,000.
4. tRNA genes are transcribed by RNA pol III but not by RNA pol II.
5. The fidelity of RNA pol II refers to the enzyme's ability to select the correct nucleotide to add to the growing RNA chain.
6. RNA pol II is a highly conserved enzyme because of Human genes encoding 10 of the 12 subunits can substitute for their yeast counterparts.
7. The figure is not visible
8. Transcription in initiation in eukaryotes is a complicated process involving the orchestrated sequential binding of many proteins. True
Several general transcription factors including the TATA-binding protein bind specifically to the promoter. True
These transcription factors allow the recruitment of RNA polymerase II, followed by binding of additional factors to produce the closed initiation complex. True
The complex is converted into the open initiation complex by the helicase activity of one of these transcription factors.True
Phosphorylation of the polymerase results in a conformational change converting the polymerase into its elongation mode. True.
9. None of the eukaryotic RNA polymerases recognizes prokaryotic promoters.
10. They have three distinct RNA polymerases. True
Their mRNAs are generally synthesized by RNA polymerase I. False (RNA Pol II does it)
RNA polymerase III synthesizes only rRNAs. False (Pre-tRNA and SnRNA also synthesised)
The tRNAs are synthesized by RNA polymerase II. False
Eukaryotic RNA polymerases are homologous to each other and to bacterial RNA polymerases. True
11. The CTD is critical for viability.
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