Deck 9: Post-Transcriptional Gene Control

Question 1

Which process involves two transesterification reactions?

A)splicing
B)RNA editing
C)capping
D)nuclear transport

Answer 1

A

Question 2

Histone mRNAs lack

A)poly(A)tails.
B)introns.
C)a 3´UTR.
D)all of the above

Answer 2

D

Question 3

This type of RNA functions in the removal of introns from pre-RNAs.

A)snRNA (small nuclear RNA)
B)snoRNA (small nucleolar RNA)
C)siRNA (small interfering RNA)
D)miRNA (micro RNA)

Answer 3

A

Question 4

The export of mRNAs outside the nucleus requires several proteins that are post-translationally modified by:

A)acetylation.
B)methylation.
C)phosphorylation.
D)ubiquitination.

Question 5

Indicate the order in which the following steps occur in the production of a mature mRNA.

A)initiation of transcription,splicing,addition of 5´ cap,addition of poly(A)tail,transport to cytoplasm
B)initiation of transcription,addition of 5´ cap,splicing,addition of poly(A)tail,transport to cytoplasm
C)initiation of transcription,addition of poly(A)tail,addition of 5´ cap,splicing,transport to cytoplasm
D)initiation of transcription,addition of 5´ cap,addition of poly(A)tail,splicing,transport to cytoplasm

Question 6

In an experiment you have used recombinant DNA technology to create hnRNP C protein tagged with green fluorescent protein and hnRNP A1 protein tagged with red fluorescent protein.What would you expect to see when the proteins are expressed and visualized in Xenopus cells?

A)green fluorescence only in the cytoplasm
B)red fluorescence only in the nucleus
C)red fluorescence only in the cytoplasm
D)green and red fluorescence in the nucleus

Question 7

pre-mRNPs that are capped,spliced,and cleaved must be _____ before they are called nuclear mRNPs.

A)elongated
B)phosphorylated
C)polyadenylated
D)transcribed

Question 8

The RNA recognition motif is the most common RNA-binding domain in hnRNP proteins.Another name for this motif is:

A)RNA-binding domain.
B)RNA motif.
C)KH motif.
D)all of the above

Question 9

Components of the spliceosome include

A)a pre-mRNA
B)proteins that react immunologically with the sera of patients with systemic lupus erythematosus.
C)U1 snRNA,which interacts with the 5´ splice site in pre-mRNA.
D)all of the above

Question 10

Splice sites in pre-mRNA are marked by two universally conserved sequences located

A)in the middle of introns.
B)at the ends of exons.
C)at the ends of introns.
D)none of the above

Question 11

Splicing joins

A)two intron sequences.
B)two polypeptides.
C)two DNA molecules.
D)two exon sequences.

Question 12

Sex-lethal protein in Drosophila can best be described as a(n)

A)splicing regulatory factor.
B)RNA editing factor.
C)transcription factor.
D)all of the above

Question 13

Which of the following does not require enzymes?

A)RNA editing
B)excision of group II introns
C)trans-splicing
D)excision of group III introns

Question 14

Mutations that affect the binding of an SR protein to an exonic splicing enhancer can cause exon skipping in some genes,producing mRNAs that when translated yield nonfunctional proteins.In addition to an RNA-binding domain,SR proteins also contain an RS domain that is involved in binding:

A)DNA.
B)RNA.
C)protein.
D)none of the above

Question 15

RNA editing is

A)post-transcriptional alteration of mRNA sequences.
B)pretranscriptional alteration of RNA sequences.
C)post-transcriptional joining of two RNA molecules.
D)none of the above

Question 16

Sequencing of small RNAs isolated from metazoan cells revealed low levels of short,capped
RNAs transcribed from both the sense and antisense strands of DNA.What is the term used to describe the fact that the majority of the metazoan genome is transcribed?

A)permissive transcription.
B)persuasive transcription.
C)pervasive transcription.
D)progressive transcription.

Question 17

Some _____ have evolved a constitutive transport element within their genome,which allows for the export of unspliced RNAs into the cytoplasm.

A)nematodes
B)mammals
C)retroviruses
D)trypanosomes

Question 18

The consensus sequence for poly(A)addition is

A)the site of poly(A)tail addition.
B)AAUAAA.
C)downstream of the cleavage site.
D)none of the above

Question 19

In birds,a gene encoding a Ca²⁺-activated K⁺ channel is expressed in auditory hair cells as multiple mRNAs,which encode for proteins that open at different Ca²⁺ concentrations.The Ca²⁺ concentration at which the channel opens allows these cells to respond to different sound frequencies.Which one of the following would explain the appearance of the various isoforms of this particular channel?

A)the presence of chain-terminating mutations
B)exon skipping
C)the absence of compensating mutations
D)alternative splicing

Question 20

The branch-point A residue involved in lariat formation is part of the

A)intron.
B)exon.
C)5´'UTR.
D)3´UTR.

Question 21

Which of the following does not take part in the degradation process of eukaryotic mRNAs?

A)capping
B)endonucleolytic cleavage
C)exonucleolytic decay
D)poly(A)shortening

Question 22

Cells use several ways to avoid the translation of improperly processed mRNA molecules._____ is(are)considered mRNA surveillance mechanisms.

A)Nonsense-mediated decay
B)Non-stop decay
C)No-go decay
D)all of the above

Question 23

Knocking out the dicer gene in mammals would lead to a loss of:

A)mRNAs.
B)miRNAs.
C)shRNAs.
D)snRNAs.

Question 24

Which type of RNA participates in nuclear export of mRNA?

A)snRNA
B)hnRNA
C)tRNA
D)rRNA

Question 25

The RISC complex contains which one of the following proteins?

A)Argonaute
B)DGCR8
C)Dicer
D)Drosha

Question 26

The mammalian target of rapamycin (mTOR)complex 1 plays an integral role in all but one of these processes.Which one is mTOR not directly involved in?

A)Pol III transcription
B)protein degradation
C)ribosome biogenesis
D)promoting cell growth

Question 27

How is the 5´ cap added to nascent RNAs?

Question 28

Transport of unspliced HIV mRNA from the nucleus to the cytoplasm of host cells is promoted by a virus-encoded protein named

A)Tat.
B)Rev.
C)nucleoplasmin.
D)Ran.

Question 29

The 45S pre-rRNA molecule

A)can organize a nucleolus when present in a single copy.
B)is encoded by tandemly arranged genes.
C)is methylated on specific bases.
D)all of the above

Question 30

A ribozyme is an RNA sequence

A)that uses Mg²⁺ ions as a cofactor.
B)with catalytic ability to cleave RNA.
C)that acts in the spliceosome.
D)all of the above

Question 31

The cell contains numerous organelles,all with specific functions,but the one that plays a key role in the digestion of ribosomes,mitochondria,and other organelles is the:

A)autophagosome.
B)endosome.
C)nucleosome.
D)proteasome.

Question 32

Which of these events does not occur within the nucleus?

A)RNA editing in mammals
B)RNA capping
C)polyadenylation
D)RNA editing in protozoans

Question 33

Which of the following regarding the P-body is FALSE?

A)it contains decapping enzymes
B)it is a deadenylase complex
C)it has exoribonuclease activity
D)it is the site where polysomes form

Question 34

What are hnRNP proteins? How were they identified?

Question 35

In animal cells,nearly all cytoplasmic mRNAs have a 3´ poly(A)tail,which is added to the pre-mRNA before splicing.What proteins are involved in polyadenylation? Indicate their order of association with pre-mRNA and their functions.

Question 36

snRNP-dependent splicing of pre-mRNA is thought to have evolved from the self-splicing properties inherent in the sequence of either group I or II introns.Alternative splicing of pre-mRNAs processed by spliceosomes has been demonstrated,whereas this phenomenon does not occur in RNA transcripts that undergo self-splicing.Explain this difference.

Question 37

Synthesis of pre-rRNA occurs in the

A)nucleolus.
B)endoplasmic reticulum.
C)extranucleolar area of the nucleus.
D)cytosol.

Question 38

Which of the following are NOT found within the nucleus?

A)Cajal bodies
B)histone locus bodies
C)nucleoli
D)P-bodies

Question 39

microRNAs play a key role in which of the following?

A)translational repression
B)viral RNA degradation
C)RNA interference
D)all of the above

Question 40

You are using a variety of techniques to study how the RISC complex differs between siRNAs and miRNAs and have found that what distinguishes an RISC complex containing an siRNA from one containing an miRNA is that:

A)the miRNA base-pairs perfectly with its target mRNA.
B)the siRNA base-pairs perfectly with its target mRNA.
C)the miRNA-RISC complex inhibits transcription.
D)the siRNA-RISC complex blocks translation.

Question 41

In yeast,U2 snRNA base-pairs to a short sequence near branch-point A in introns.In higher eukaryotes,this branch-point sequence is not highly conserved,and a protein called U2AF promotes binding of U2 snRNA to pre-mRNA.You have produced mice with a knockout mutation in the U2AF gene.Would you expect mice heterozygous for the U2AF knockout mutation to be viable? Would you expect mice homozygous for the U2AF knockout mutation to be viable?

Question 42

How do researchers visualize the cellular locations of specific RNA molecules?

Question 43

The tissue-specific expression of antisense RNA is one experimental approach for selectively shutting down production of a protein.For example,some researchers have proposed that this approach could be used to regulate the production of pollen in tobacco,oilseed rape,and maize.The controlled production of sterile male plants,for example,would eliminate the problem of self-fertilization in the production of hybrid maize seeds.In this approach,expression of antisense RNA would be controlled by coupling it to a promoter that is specific to anthers,the part of flowers where pollen is produced.Alternatively,the RNase activity inherent in self-splicing RNA might provide a sequence-specific means to regulate pollen production.Discuss how a catalytic RNA (i.e. ,a ribozyme)might be designed to prevent the expression of proteins needed for pollen production.

Question 44

The finding that the short consensus sequence at the 5´ end of introns is complementary to a sequence near the 5´ end of U1 snRNA suggested that this snRNA must interact with pre-mRNA for splicing to occur.Describe three types of experimental evidence that indicate U1 snRNA is required for splicing.

Question 45

The oocytes of multicellular animals contain stored mRNAs that encode numerous proteins required for early embryonic development.These proteins,however,are not translated until after fertilization and,therefore,a mechanism must be in place to ensure the stored mRNAs remain intact and untranslated before they are needed.Discuss the mechanism that keeps these stored mRNAs from being translated in the oocyte.

Question 46

Describe how the Sex-lethal (Sxl)protein is regulated during the development of Drosophila females.

Question 47

How does HIV bypass the normal restriction that prevents unspliced mRNAs from being transported from the nucleus to the cytoplasm?

Question 48

What are the main features of splicing pre-tRNAs that distinguish it from splicing pre-mRNAs?

Question 49

The spliceosomal splicing cycle involves ordered interactions among a pre-mRNA and several U snRNPs.According to the current model of spliceosomal splicing,which intermediate(s)in the splicing of a pre-mRNA containing one intron should be immunoprecipitated by anti-U2 snRNP? Which additional intermediate(s)should be immunoprecipitated by anti-U2AF?