Q: Which equation best represents the overall process of group I intron self-splicing?

$$\text{Precursor RNA} \xrightarrow{\text{2 transesterification reactions}} \text{Mature RNA} + \text{Excised intron}$$

Question 1

Which of the following best describes the mechanism by which group I introns are removed from RNA transcripts?

Accepted Answer

They are removed by a self-splicing mechanism involving two transesterification reactions.

Question 2

What is the primary role of s n R N Ps in the spliceosome-mediated splicing of pre-m R N A?

Accepted Answer

They provide the catalytic activity necessary for the excision of introns and formation of the lariat structure.

Question 3

Which of the following is a distinguishing feature of the spliceosomal intron removal mechanism, as shown in Figure 12-12?

Accepted Answer

Formation of a lariat structure during splicing.

Question 4

In which cellular organelles is self-excision of introns most commonly observed?

Accepted Answer

Mitochondria and chloroplasts

Question 5

Which of the following best describes RNA editing?

Accepted Answer

The posttranscriptional insertion, deletion, or substitution of nucleotides in an RNA molecule.

Question 6

A mutation in a plant's mitochondrial genome leads to the inability to perform substitution editing. Which process is most likely to be directly affected?

Accepted Answer

Alteration of individual nucleotide bases in mitochondrial RNA

Question 7

Which equation best represents the overall process of group I intron self-splicing?

Accepted Answer

$$	ext{Precursor RNA} \xrightarrow{	ext{2 transesterification reactions}} 	ext{Mature RNA} + 	ext{Excised intron}$$

Question 8

Which of the following is NOT a function of the spliceosome?

Accepted Answer

Editing nucleotide sequences by insertion or deletion

Question 9

In bacteria, which enzyme is primarily responsible for the removal of introns from t R N A?

Accepted Answer

Endonuclease

Question 10

A researcher observes that after splicing, an RNA molecule contains a circularized intron. Which splicing mechanism most likely produced this result?

Accepted Answer

Spliceosome-mediated splicing with lariat formation

Question 11

Which of the following statements about group II introns is correct?

Accepted Answer

They self-splice via a lariat intermediate, similar to spliceosomal introns.

Question 12

Which process is most likely to be disrupted if s n R N Ps are nonfunctional in a eukaryotic cell?

Accepted Answer

Spliceosome-mediated removal of pre-m R N A introns

Question 13

Which of the following best explains why RNA editing is considered a posttranscriptional process?

Accepted Answer

It modifies the RNA sequence after transcription but before translation.

Question 14

A mutation prevents the formation of the lariat structure during splicing. Which step in the spliceosome-mediated mechanism is most directly affected?

Accepted Answer

Branch point attack on the 5' splice site

Question 15

Which of the following is a key difference between group I and group II intron self-splicing mechanisms?

Accepted Answer

Group I introns require a guanosine cofactor, while group II introns form a lariat intermediate.

Question 16

Which of the following best describes the outcome of insertion/deletion RNA editing?

Accepted Answer

Nucleotides are added or removed, altering the total number of bases in the RNA.

Question 17

Which of the following equations best represents the two-step transesterification reaction in group I intron self-splicing?

Accepted Answer

$$	ext{Step 1:} \quad 	ext{G-OH} + 	ext{Intron-Exon} ightarrow 	ext{G-Intron} + 	ext{Exon}$$
$$	ext{Step 2:} \quad 	ext{Exon-OH} + 	ext{Exon} ightarrow 	ext{Exon-Exon} + 	ext{Intron}$$

RNA Splicing Mechanisms and RNA Editing

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