Mo Bio - Chapter 16

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.

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 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.

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 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.

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

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 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.

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 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.

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 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

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 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.

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.

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.

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

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