Mol Bio Ch 16

The nucleophile of the first step of spliceosome-mediated pre-mRNA splicing is the: A. 2' hydroxyl of the branch point adenosine. B. 3' hydroxyl of a free guanine nucleotide. C. 3' hydroxyl of the 5' splice site exon. D. 2' hydroxyl of the 3' splice site intron.

2' hydroxyl of the branch point adenosine.

Which of the following type of reaction is not involved in the spliceosome-mediated pre-mRNA splicing? A. ligation B. deamination C. transesterification D. phosphodiester bond cleavage

B. deamination

Which of the following is true of introns? A. RNA II polymerase transcribes the intron sequences along with exon sequences. B. More DNA of the human genome is devoted to exons than to introns. C. Introns are not found in bacteria or archaea, only eukaryotes. D. When annealing mature mRNA to corresponding chromosomal DNA sequences, the mRNA will form loops with intron sequences looped out.

A. RNA II polymerase transcribes the intron sequences along with exon sequences.

RNA processing that chemically alters the mRNA sequence is called: A. RNA editing. B. alternative splicing. C. RNA transformation. D. RNA modification.

A. RNA editing.

During the process of eukaryotic mRNA degradation, all of the following occur except: A. The poly(A) tail is lengthened. B. The 5' cap is removed. C. The exosome degrades the molecule to component nucleotides. D. Localization to processing bodies occurs.

A. The poly(A) tail is lengthened.

Which of the following is not true of the reactions that methylate the 5' end of the primary mRNA transcripts? A. The reaction occurs after the entire transcript is synthesized. B. The methyl groups are derived from S-adenosylmethionine. C. The enzymes that catalyze the reactions are guanylyltransferases. D. The enzymes that catalyze the reactions are associated with the C-terminal domain of RNA polymerase II.

A. The reaction occurs after the entire transcript is synthesized.

The enzyme adenosine deaminase acting on RNA (ADAR) catalyzes which of the following nucleotide conversions? A. adenosine to inosine B. adenosine to cytidine C. adenosine to guanosine D. thymidine to uridine

A. adenosine to inosine

Pre-mRNA splice sites are recognized by the spliceosome through: A. base pairing with snRNAs. B. site-specific recognition by the Sm proteins. C. RNA hairpin recognition. D. the specific distance of the intron from the mRNA 5' cap.

A. base pairing with snRNAs.

Which of the following nuclear RNA transport events requires the action of a guanine exchange factor (GEF)? A. importin release of RNA in the nucleus B. exportin release of RNA in the cytoplasm C. importin binding of RNA in the cytoplasm D. exportin binding of RNA in the nucleus

A. importin release of RNA in the nucleus

Which of the following RNAs use a Ran-independent pathway for the transport of RNA across the nuclear membrane? A. mRNA B. tRNA C. rRNA D. snRNA E. miRNA

A. mRNA

Which of the following proteins is not associated with the C-terminal domain of RNA polymerase II? A. cap binding complex B. RNA-editing terminal uridylyl-transferase C. guanylyltransferase D. polyadenylation factors

B. RNA-editing terminal uridylyl-transferase

Which of the following characteristics of group I intron splicing is not true of group II intron splicing? A. Splicing occurs without ATP. B. The first nucleophile is a 3' hydroxyl. C. Catalysis does not require a protein. D. Proteins mediate pre-RNA conformation in vivo.

B. The first nucleophile is a 3' hydroxyl.

In spliceosome-mediated pre-mRNA splicing: A. U2 snRNA base pairs to both sides of the of the splice junction. B. U2 and U6 snRNAs base pair during the two transesterification reactions. C. U6 snRNA base pairs to the 3' end of the intron. D. U5 snRNA base pairs to the 3' end of the intron.

B. U2 and U6 snRNAs base pair during the two transesterification reactions.

An RNA processing event that frequently leads to different protein products encoded by a single gene is: A. transcription. B. alternative splicing. C. alternative transcription. D. polyadenylation.

B. alternative splicing.

RNA editing by nucleotide insertion and deletion is catalyzed by the: A. spliceosome. B. editosome. C. deletosome. D. RNase A enzyme.

B. editosome.

The ribonucleoprotein, RNase P, catalyzes the: A. exonucleolytic removal of the 3' end of tRNA molecules. B. endonucleolytic removal of the 5' end of tRNA molecules. C. ATP-independent removal of tRNA introns. D. degradation of the poly(A) tail.

B. endonucleolytic removal of the 5' end of tRNA molecules.

The noncoding regions of a primary mRNA transcript that interrupt coding regions are known as: A. exons. B. introns. C. poly(A) tails. D. 5' caps.

B. introns

The transport receptor, exportin, transports: A. mRNA to the nucleus when associated with GDP-bound Ran protein. B. mRNA to the cytoplasm when associated with GTP-bound Ran protein. C. noncoding RNA to the nucleus when associated with GDP-bound Ran protein. D. mRNA to the cytoplasm when associated with GDP-bound Ran protein.

B. mRNA to the cytoplasm when associated with GTP-bound Ran protein.

Small regulatory RNAs are known to be: A. bound by Drosha in the cytoplasm. B. recognized by DGCR8 in the nucleus. C. cleaved by Dicer in the nucleus. D. transported to the nuclease as fully processed miRNA.

B. recognized by DGCR8 in the nucleus.

The main reason that mRNA transcripts are modified at the 5' and 3' ends is: A. to ensure that all nucleotides are phosphorylated. B. to protect the RNA from nucleolytic degradation. C. so that the two ends remain associated with each other during transport. D. to guide the removal of introns.

B. to protect the RNA from nucleolytic degradation.

The nucleophile of the second step of spliceosome-mediated pre-mRNA splicing is the: A. 2' hydroxyl of the branch point adenosine. B. 3' hydroxyl of a free guanine nucleotide. C. 3' hydroxyl of the 5' splice site exon. D. 2' hydroxyl of the 3' splice site intron.

C. 3' hydroxyl of the 5' splice site exon.

The chemical structure of the 5' mRNA cap includes ______________ covalently linked to the 5' terminal residue of the mRNA through a ______________ linkage. A. 7-methylguanosine / 5' to 3' phosphodiester B. N-formyladenosine / 5' to 3' diphosphate C. 7-methylguanosine / 5' to 5' triphosphate D. 7-methylcytosine / 5' to 5' phosphodiester

C. 7-methylguanosine / 5' to 5' triphosphate

Which of the following reflects sequence elements conserved in pre-mRNA splice sites? A. CTAG at the 3' end of the 5' exon B. GAAG at the 3' end of the intron C. AG at the 5' end of the intron D. G at the 5' end of the 3' exon

C. AG at the 5' end of the intron

A scientist evaluates cellular mRNA and finds a population of transcripts that do not have a 3' poly(A) tail. However, these transcripts are translated into protein. What would these proteins most likely be? A. ribosomal proteins B. RNA binding proteins C. DNA binding proteins D. transport proteins.

C. DNA binding proteins

Which proteins are bound at the exon-exon borders and facilitate transport of the spliced mRNA from the nucleus to the cytoplasm? A. exportins B. karyopherins C. MAGOH and eIF4AIII D. Ran-GTP complex E. U1

C. MAGOH and eIF4AIII

A ribozyme is an: A. enzyme that degrades mRNA. B. enzyme that chemically modifies tRNA base composition. C. RNA molecule with enzymatic activity. D. RNA molecule that guides a protein enzyme to the correct sequence.

C. RNA molecule with enzymatic activity.

A scientist identifies a cell line derived from muscle with reduced expression of several muscle-specific proteins including α-actin and myosin. Further investigation shows that while mRNA specific to these proteins is transcribed and polyadenylated at normal rates, the half-life of the mRNAs is significantly lower. What would be a likely explanation? A. There is a mutation in RNA polymerase II. B. There is an increase in RNA-editing terminal uridylyltransferase (TUTase) activity. C. There is a mutation in poly(A) binding protein (PABP). D. There is a mutation in polyadenylate polymerase (PAP). E. There is an increase in number of processing bodies.

C. There is a mutation in poly(A) binding protein (PABP).

Which of the following events do not occur during spliceosome assembly on pre-mRNAs? A. U1 snRNP binds to the 5' splice site. B. U2 snRNP binds to the branch point. C. U6 snRNP binds to the 3' splice site. D. U5 snRNP binds to the 5' splice site.

C. U6 snRNP binds to the 3' splice site.

Which of the following is not a common posttranscriptional modification of tRNA molecules? A. removal of nucleotides from the 5' and 3' ends B. methylation and deamination of specific bases C. addition of a 5' cap D. attachment of the C-5 of uracil to the ribose at specific sequences

C. addition of a 5' cap

Poly(A) site choice: A. is a mechanism to determine the length of the poly(A) tail. B. leads to polyadenylation of the 5' end of the mRNA. C. can generate multiple protein products from a single gene. D. is catalyzed by small nucleolar ribonucleoproteins.

C. can generate multiple protein products from a single gene.

Which of the following is not an enzymatic function of the editosome? A. uridylyltransferase B. ligase C. deaminase D. exoribonuclease

C. deaminase

Which of the following eukaryotic RNA processing events does not occur in the nucleus? A. intron splicing B. polyadenylation C. degradation of mRNA D. RNA editing

C. degradation of mRNA

Which of the following is a typical example of mRNA editing? A. deamination of cytidine to thymine B. insertion of one or more A residues C. deletion of one or more U residues D. guanosine deaminated to inosine

C. deletion of one or more U residues

In order to isolate proteins that interact with Ran, a student plans to perform a series of coprecipitation experiments. She first isolates nuclei from cells, and then performs the immunoprecipitation assay. Which protein(s) are most likely to coprecipitate with Ran? A. exportin B. importin C. exportin and importin D. MAGOH E. MAGOH and Y14

C. exportin and importin

As scientists began to purify and analyze RNA, it became apparent that rRNA and tRNA were modified. Which technique allowed them to separate the various nucleotides so they could analyze the modifications? A. polyacrylamide electrophoresis B. agarose gel electrophoresis C. thin-layer chromatography D. sucrose gradient centrifugation E. mass spectrophotometry

C. thin-layer chromatography

RNA processing that leads to mRNAs in which exon sequences are derived from different primary transcripts is called: A. alternative splicing. B. poly(A) site choice. C. trans-splicing. D. group I self-splicing.

C. trans-splicing.

Which of the following statements about mRNAs and microRNAs is false? A. Both are transcribed by RNA Pol II. B. Both are capped and polyadenylated. C. Both undergo nucleolytic cleavage in the nucleus and the cytoplasm. D. Both are processed via interaction with snoRNPs.

D. Both are processed via interaction with snoRNPs.

Polyadenylation of mRNA requires all of the following except: A. Pol II extends the transcript beyond the site where the poly(A) tail is added. B. The site of poly(A) addition is marked by specific sequence elements in the transcript. C. The transcript is cleaved by an endonuclease that associates with the C-terminal domain of Pol II. D. Polyadenylate polymerase uses a poly(U) RNA template to synthesize the poly(A) tail.

D. Polyadenylate polymerase uses a poly(U) RNA template to synthesize the poly(A) tail.

Which of these processes is least likely to expand the coding capacity of the genome? A. RNA editing B. alternative splicing C. poly(A) site choice D. RNA capping

D. RNA capping

All of the following evidence supports the RNA world hypothesis except: A. RNA can function as a genome. B. An RNA component of ribosomes catalyzes the synthesis of proteins. C. RNA can serve a structural role. D. RNA stabilizes membranes. E. RNA regulates gene expression.

D. RNA stabilizes membranes.

10. In an experiment similar to that performed by Shatkin and colleagues, a student synthesized mRNAs such that 32P-GTP was incorporated; 7-meG labeled with 3H was used to cap the mRNA. A fraction of the sample was run on a gel and confirmed that radiolabeled capped transcripts had indeed been produced. The remainder of mRNA was incubated with wheat germ cell extract to allow binding to ribosomes. The sample was deposited at the top of a sucrose density gradient and spun in a centrifuge. Surprisingly, neither label comigrated with the ribosome fraction; the ribosomes did migrate as expected. What is the most likely reason for this result? A. The ribosomes did not incorporate the 3H label. B. The sucrose gradient was not made correctly. C. The wheat germ was contaminated with guanylyltransferase. D. The wheat germ was contaminated with RNase E. The centrifuge did not spin at the correct speed.

D. The wheat germ was contaminated with RNase

A ribonucleoprotein is: A. an enzyme that degrades RNA. B. an RNase that functions in the nucleus. C. a nucleotide-transport protein. D. a noncoding RNA complexed with protein.

D. a noncoding RNA complexed with protein.

A student is studying the localization of mRNA in the cell. The cells are treated with a monoclonal antibody to a protein contributing to processing (P) body structure. Which part(s) of the cell would most likely show immunofluorescence? A. nucleus B. cytoplasm C. both nucleus and cytoplasm D. cannot be determined

D. cannot be determined

The mRNA that would most likely have the longest half-life would: A. contain an exon junction complex bound downstream of a stop codon. B. lack a stop codon. C. contain an AU-rich element in the 3'-UTR. D. contain one or more hairpin structures.

D. contain one or more hairpin structures.

Szostak and colleagues found that a ribozyme found in the human genome was related to a similar enzyme in human hepatitis delta virus (HDV). In order to identify this ribozyme, they: A. searched the published human genome sequence for HDV sequences. B. searched the published human genome sequence for ribozyme sequences. C. incubated HDV RNA and evaluated the sample for ribozyme activity. D. incubated human RNA and evaluated the sample for ribozyme activity.

D. incubated human RNA and evaluated the sample for ribozyme activity.

Which of the following is not usually involved in the processing of primary mRNA transcripts? A. addition of multiple adenosines to the 3' end B. covalent joining of exons C. methylation of nucleotides at the 5' end D. insertion of intron sequences

D. insertion of intron sequences

A highly branched secondary structure is formed during: A. attachment of a 5' cap to mRNA. B. attachment of poly(A) tails to mRNA. C. splicing of all classes of introns. D. splicing of group I and II introns.

D. splicing of group I and II introns.

Differential RNA processing may result in: A. a shift in the ratio of mRNA produced from two adjacent genes. B. inversion of certain exons in the mature mRNA. C. the production of the same protein from two different genes. D. the production of two proteins with different activities from a single gene.

D. the production of two proteins with different activities from a single gene.

In prokaryotes, the 30S pre-rRNA transcript is cleaved into: A. two rRNAs. B. three RNAs. C. two rRNAs and tRNA. D. three RNAs and tRNA. E. multiple copies of three specific RNAs plus tRNA.

D. three RNAs and tRNA.

Small guide RNAs (gRNA) of the editosome complex: A. are complementary to a target sequence in the pre-edited RNA. B. are only found in the nucleus. C. acquire sequence differences copied from pre-mRNA. D. typically contain a 3' terminal oligo(U) extension.

D. typically contain a 3' terminal oligo(U) extension.

TREX (transcription export) is responsible for: A. splicing of mRNA. B. transport of mRNA. C. editing of mRNA. D. degradation of mRNA. E. A and B

E. A and B

What category of enzyme adds a CCA to the 3' OH of tRNAs? A. uridylyltransferase B. glycosyltransferase C. ligase D. guanylyltransferase E. nucleotidyltransferase

E. nucleotidyltransferase

snoRNPs are found in the nucleolus. Two functions of these complexes include: A. rRNA processing. B. tRNA processing. C. adding methyl groups to rRNA. D. adding methyl groups to tRNA. E. transcription of 5S rRNA. F. A and C

F. A and C

Which of the following are characteristics of ribozymes? Select one or more that apply. A. cleavage of phosphodiester bonds B. loss of activity at higher temperatures C. self-splicing D. removal of nucleotides from precursor RNAs E. found in eukaryotes, not bacteria F. All except E

F. All except E