Question 1

Which of the following best describes the role of Xrn1 in mRNA degradation?

Accepted Answer

Xrn1 is an exonuclease that degrades mRNA from the 5' end after decapping.

Question 2

Which process is activated when the polyA tail of mRNA is still intact?

Accepted Answer

Decapping-independent degradation

Question 3

What is the function of the RISC complex in microRNA-mediated silencing?

Accepted Answer

It loads miRNA and targets complementary mRNA for degradation or translational repression.

Question 4

Which of the following is TRUE about microRNAs (miRNAs)?

Accepted Answer

miRNAs are typically about 22 nucleotides long after processing.

Question 5

A mutation in the Drosha gene would most likely affect which cellular process?

Accepted Answer

Processing of pri-miRNA to pre-miRNA

Question 6

Which of the following statements about mRNA degradation pathways is correct?

Accepted Answer

Degradation pathways can target specific subsets of mRNAs based on sequence elements.

Question 7

In the context of RNA interference (RNAi), which equation best represents the relationship between miRNA and target mRNA?

Accepted Answer

$$miRNA + mRNA \rightarrow RISC \rightarrow mRNA\ degradation$$

Question 8

Which of the following is a consequence of miRNA binding to a target mRNA with perfect complementarity?

Accepted Answer

Endonucleolytic cleavage and degradation of the mRNA

Question 9

Which pathway is most likely to be activated when the polyA tail of an mRNA is removed?

Accepted Answer

Deadenylation-dependent decapping

Question 10

A researcher finds that a specific mRNA is rapidly degraded in the presence of a certain miRNA. Which mechanism is most likely responsible?

Accepted Answer

miRNA-mediated silencing via RISC complex

Question 11

Which of the following is NOT a step in the microRNA pathway?

Accepted Answer

Direct translation of miRNA into protein

Question 12

Which equation best represents the process of deadenylation-dependent mRNA degradation?

Accepted Answer

$$mRNA \xrightarrow{deadenylation} decapping \xrightarrow{Xrn1} degradation$$

Question 13

Which of the following is a real-world implication of miRNA dysregulation?

Accepted Answer

It can lead to the development of certain diseases, including cancer.

Question 14

Which of the following statements about RNA-induced silencing complex (RISC) is correct?

Accepted Answer

RISC binds to miRNA and targets mRNA for degradation or translational repression.

Question 15

Which of the following is required for deadenylation-independent decapping of mRNA?

Accepted Answer

The polyA tail must be intact.

Question 16

Which of the following best explains why some mRNAs are degraded faster than others?

Accepted Answer

They contain specific sequence elements that are recognized by degradation pathways.

Question 17

Which of the following is a key difference between deadenylation-dependent and deadenylation-independent mRNA degradation?

Accepted Answer

Deadenylation-dependent degradation requires removal of the polyA tail before decapping.

Question 18

Which of the following is most likely to occur if a mutation prevents the formation of the RISC complex?

Accepted Answer

miRNA-mediated silencing of target mRNAs would be impaired.

Question 19

Which of the following is a correct sequence of events in miRNA-mediated mRNA degradation?

Accepted Answer

Transcription of miRNA gene $$\rightarrow$$ Processing by Drosha $$\rightarrow$$ Loading into RISC $$\rightarrow$$ Target mRNA degradation

RNA Stability and Degradation: Mechanisms and Regulation

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