Question 1

Which of the following best describes the role of the RNA-induced silencing complex (RISC) in microRNA (miRNA) mediated gene regulation?

Accepted Answer

RISC binds to miRNA and guides it to complementary mRNA sequences, leading to mRNA degradation or translational repression.

Question 2

Which pathway is activated when the polyA tail of an mRNA is still intact, leading to mRNA degradation?

Accepted Answer

Deadenylation-independent pathway

Question 3

A mutation in the Drosha enzyme would most likely affect which step in the microRNA pathway?

Accepted Answer

Cleavage of pri-miRNA into pre-miRNA

Question 4

Which of the following is TRUE regarding the specificity of miRNA-mediated silencing?

Accepted Answer

miRNAs can regulate many mRNAs by binding to partially complementary sequences, often in the 3' UTR.

Question 5

Which of the following diseases is most likely to be associated with dysregulation of miRNA pathways?

Accepted Answer

Cancer

Question 6

Which equation correctly represents the relationship between the number of possible codons and the number of nucleotide choices per position in the genetic code?

Accepted Answer

$$N_{codons} = 4^3$

Question 7

In eukaryotes, which sequence is recognized by the ribosome to initiate translation?

Accepted Answer

Kozak sequence

Question 8

Which of the following statements about the initiation of translation in prokaryotes is CORRECT?

Accepted Answer

The Shine-Dalgarno sequence helps position the ribosome at the correct start codon.

Question 9

Which of the following best explains why the sedimentation rate (Svedberg unit, S) of ribosomal subunits is not directly additive?

Accepted Answer

The S value reflects size, density, and shape, so when subunits combine, their sedimentation rates do not simply add.

Question 10

A researcher is studying a mutation that prevents the addition of the polyA tail to mRNA. Which mRNA degradation pathway would be most affected?

Accepted Answer

Deadenylation-dependent pathway

Question 11

During translation elongation, which factor is responsible for bringing aminoacyl-tRNA to the A site in prokaryotes?

Accepted Answer

EF-Tu

Question 12

Which of the following antibiotics mimics aminoacyl-tRNA and can cause premature termination of translation?

Accepted Answer

Puromycin

Question 13

Which of the following is a key difference between translation initiation in prokaryotes and eukaryotes?

Accepted Answer

Eukaryotes use a 5' cap and Kozak sequence for ribosome binding, while prokaryotes use the Shine-Dalgarno sequence.

Question 14

Which of the following correctly describes the polarity of a polypeptide chain?

Accepted Answer

Polypeptides are synthesized from the N-terminus to the C-terminus.

Question 15

Which equation represents the number of possible amino acids encoded by a codon, given four nucleotide choices and three positions?

Accepted Answer

$$N_{amino	ext{ }$$acids} = $$4^3$$

Question 16

Which of the following is TRUE about the function of EF-G in prokaryotic translation?

Accepted Answer

EF-G promotes translocation of the ribosome along the mRNA.

Question 17

A scientist observes that a certain mRNA is degraded even though its polyA tail is intact. Which pathway is most likely responsible?

Accepted Answer

Deadenylation-independent pathway

Question 18

Which of the following statements about miRNA is CORRECT?

Accepted Answer

miRNAs are transcribed from miRNA genes and processed to about 22 nucleotides.

Question 19

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 20

Which of the following best explains why multiple Shine-Dalgarno sequences can be found on a single prokaryotic mRNA?

Accepted Answer

Each Shine-Dalgarno sequence allows for the translation of a different protein from the same mRNA (polycistronic mRNA).

RNA Stability, mRNA Degradation, and Translation: Mechanisms and Regulation

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