Chapter 38 RNA Processing in Eukaryotes
Matching Questions
Use the following to answer questions 1–10:
Choose the correct answer from the list below. Not all of the answers will be used.
a) poly(A) tail
b) methylation
c) alternative splicing
d) spliceosome
e) U2 and U6
f) U4, U5, and U6
g) spliced
h) translation
i) RNA editing
j) GU
k) ribozyme
l) RNA polymerase I
m) ATP
1.
mRNA precursors may be spliced by ______________ complexes.
2.
Nearly all mRNA precursors in higher eukaryotes are ______________.
Ans:
g
Section: Introduction
3.
______________ is an elongated sequence that stabilizes RNA.
Ans:
Section: 38.3
4.
______________ transcription gives rise to three ribosomal components.
Ans:
Section: 38.1
5.
______________ is a common rRNA modification.
Ans:
b
6.
Introns to be spliced start with this sequence of ______________.
Ans:
Section: 38.3
7.
______________ These small nuclear RNAs form the catalytic center of the spliceosome.
Ans:
Section: 38.3
Ans:
d
Section: 38.3
Chapter 38 RNA Processing in Eukaryotes
2
8.
A change, other than splicing, made to the base sequence of RNA following transcription is
called ______________.
9.
______________ is a mechanism of splicing that allows diversity in the proteins generated from
a particular gene.
Ans:
Section: 38.3
10.
An RNA molecule that is catalytic is called a(n) ______________.
Ans:
k
Section: 38.4
Fill–in-the-Blank Questions
11.
At least ____ % of all genetic diseases are caused by mutations that affect RNA splicing.
Ans: 15 Section: 38.3
12.
The small subunit of ribosomal RNA is _____ S.
Ans: 18 Section: 38.1
13.
Recognition of the 5 splice site by _____ is the first step in splicing.
Ans: U1 Section: 38.3
14.
Diversity in proteins is due to _____ of the same gene.
Ans: alternative splicing Section: 38.3
15.
Improper splicing that leads to improper hemoglobin synthesis may cause the disease known as
_____.
Ans: thalassemia Section: 38.3
16.
The enzyme _____ transcribes a single precursor that encodes for the 18S rRNA, the 28S rRNA,
and the 5.8S rRNA.
Ans: RNA polymerase I Section: 38.1
17.
RNA self-splicing demonstrates the role of RNA as a(n) _____.
Ans: catalyst Section: 38.4
18.
The immediate product of RNA polymerase II is often referred to as _____.
Ans: pre-mRNA Section: 38.4
19.
Self-splicing by RNA requires a _____ cofactor.
Ans:
Section: 38.3
Chapter 38 RNA Processing in Eukaryotes
3
Multiple-Choice Questions
20.
The percentage of diseases caused by mutations that affect mRNA splicing is
A)
2.
B)
15.
C)
20.
D)
30.
E)
None of the above.
21.
Noncoding regions of RNA are called
A)
nonsense RNA.
B)
empty RNA.
C)
intron RNA.
D)
exon RNA.
E)
precursor RNA.
Ans: C Section: Introduction
22.
RNA polymerase III is responsible for the transcription of
A)
18S rRNA.
B)
28S rRNA.
C)
tRNA.
D)
mRNA.
E)
A and B.
Ans: E Section: 38.2
23.
mRNA is transcribed by
A)
RNA polymerase I.
B)
RNA polymerase II.
C)
RNA polymerase III.
D)
All of the above.
E)
None of the above.
Ans: B Section: 38.2
24.
RNA polymerase I transcribes the genes for
A)
mRNA precursors.
B)
18S, 5.8S, and 28S rRNA.
C)
most tRNA.
D)
All of the above.
E)
None of the above.
Ans: B Section: 38.1
25.
Which of the following modifications are made to eukaryotic tRNA transcripts?
A)
modification of base and ribose moieties
B)
removal of the 3 trailer
C)
cleavage of the 5 leader by RNase P
D)
CCA is added
E)
All of the above.
Ans: E Section: 38.2
Ans: B Section: 38.3
Chapter 38 RNA Processing in Eukaryotes
4
26.
______________ is used to form cap 0 of mRNA.
A)
S-adenosylmethionine
B)
Cysteine
C)
Biotin
D)
Methanol
E)
Dimethyl-RNA methylase
27.
The polypyrimadine tract
A)
is found at the 3 end of an intron.
B)
is a consensus sequence.
C)
contains a stretch of 10 pyrimidines.
D)
All of the above.
E)
None of the above.
Ans: D Section: 38.3
28.
Diseases caused by mutations in pre-mRNA or in the splicing factors include
A)
Burkett lymphoma.
B)
thalassemia.
C)
retinitis pigmentosa.
D)
A and C.
E)
A, B, and C.
Ans: C Section: 38.3
29.
Proteins that possess alternative splicing products include
A)
antibodies.
B)
hemoglobin β.
C)
apolipoprotein.
D)
A and C.
E)
B and C.
Ans: A Section: 38.3
30.
The function of guanosine in self-splicing is
A)
to provide energy.
B)
as an attacking group.
C)
as a necessary base for RNA editing.
D)
All of the above.
E)
None of the above.
Ans: B Section: 38.4
31.
The carboxy-terminal domain (CTD) of RNA polymerase II undergoes reversible
phosphorylation during transcription. In that phosphorylation events tend to be a signal, what
does this phosphorylation event signal?
A)
Dephosphorylation signals recruiting of proteins to catalyze polyadenylation.
B)
Phosphorylation signals recognition of the “stop” codon.
C)
Dephosphorylation signals recruiting of spliceosome proteins.
D)
Phosphorylation signals the transition from transcription initiation to elongation.
E)
Dephosphorylation activates the catalytic function of ribozymes.
Ans: A Section: 38.3
Chapter 38 RNA Processing in Eukaryotes
5
32.
Why might a single base pair mutation in eukaryotic mRNA be less serious than one in
prokaryotic mRNA?
A)
If the mutation occurs in the intron, it will not affect the gene product.
B)
If the mutation occurs in a transcript with alternative splicing but not in the splice site,
only one gene product may be affected.
C)
If the mutation occurs 3’ of the start site, it will not affect the gene product.
D)
A and B
E)
A, B, and C
33.
A mutation in an enzyme that catalyzes a transesterification reaction would inhibit which of the
following events?
A)
mRNA termination
B)
polyadenylation
C)
mRNA splicing
D)
5 capping
E)
chain initiation
Ans: C Section: 38.3
34.
You read an article in a popular magazine about a unicellular plant that has DNA with catalytic
activity. Knowing that RNA can have catalytic activity, would you believe this article?
A)
Yes, DNA could easily be attacked by a guanosine cofactor.
B)
Yes, but only DNA not associated with proteins that would constrain the formation of
DNA loop structures.
C)
Yes, all that is required is a 3’OH to attack the 3’splice site.
D)
No, uracil of RNA is required in the catalytic site.
E)
No, DNA is constrained by its double helix structure and could not fold into a catalytic
structure.
Ans: E Section: 38.4
35.
Because RNA polymerase II has no proofreading function, it may provide a mechanism for
generating diversity. Explain?
A)
Small nucleolar ribonucleoproteins direct modification to form pseudouridine bases.
B)
RNA can be altered after transcription by RNA editing.
C)
Proofreading would slow down transcription, preventing cells to respond rapidly to
changing cellular demands.
D)
The 5 leader sequence is removed prior to translation. The synthesis of this extra length
of transcript is thermodynamically unsound.
E)
Several 5 caps are added to mRNA, which shifts the reading frame, depending on the
cap.
Ans: B Section: 38.3
Short-Answer Questions
36.
How is the mature 3 end of mRNA formed?
After cleavage at this site, about 250 adenylate residues are added to the 3 end of the
transcript to form the mature mRNA.
Section: 38.3
Ans: D Section: 38.3
Chapter 38 RNA Processing in Eukaryotes
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37.
Loss of a 3 polyadenylation is likely to cause what?
38.
Explain the modifications of tRNA.
there are additional splicing events before the tRNA molecules are mature.
Section: 38.2
39.
What role do small nucleolar ribonucleoproteins (snoRNPs) play in RNA processing?
reactions and the formation of pseudouridine.
Section: 38.1
40.
How are introns detected for splicing?
and ends with an AG. Also, introns have an internal splice sited called a branch site.
Section: 38.3
41.
What is the catalytic chemistry of mRNA splicing?
The 5 end of the exon is held close to the 3 end and a second transesterification occurs.
Section: 38.3
42.
Two proteins, X and Y, are highly homologous with many identical domains. However, protein
Y has two cassettes of amino acid sequences that are not found in X. Explain.
additional intron was removed from X and kept for Y.
Section: 38.3
43.
What is the function of the 5 cap on mRNA transcripts?
contributes to the stability of the mRNA molecule.
Section: 38.3
44.
Guanosine cofactor is used in what mechanism?
reactions of ribozymes.
Section: 38.4
45.
Distinguish between the 5-mRNA caps designated cap 0, cap 1, and cap 2.
Section: 38.3
Ans:
It is likely to cause a less stable mRNA and less protein expressed in the cell.
Section: 38.3
Chapter 38 RNA Processing in Eukaryotes
7
46.
Approximately how many mRNA transcripts in higher eukaryotes undergo processing?
47.
What is the role of GTP in self-splicing?
GTP serves as the transient attacking group on the 5 splice site.
Section: 38.4
48.
What is present in the spliceosome complex?
associated proteins) and the mRNA molecule to be spliced.
Section: 38.3
49.
Draw the mechanism of lariat formation in a splicing pathway.
Ans:
Details are shown in Figure 38.7.
Section: 38.3
50.
What are the two types of splicing categories?
cofactor, while Group II utilizes the 2-OH group of an intron adenylate.
Section: 38.4
Ans:
Nearly all mRNA precursors in higher eukaryotes are spliced.
Section: 38.3