Question 1

Which of the following best describes the function of the spliceosome in eukaryotic cells?

Accepted Answer

It removes introns from pre-mRNA and joins exons together.

Question 2

A mutation in the branch-site adenosine of a group II intron would most likely disrupt which step of splicing?

Accepted Answer

Nucleophilic attack on the 5' splice site by the 2' oxygen of adenosine.

Question 3

Alternative splicing increases protein diversity by:

Accepted Answer

Allowing a single gene to produce multiple mRNA isoforms that encode different proteins.

Question 4

Which equation best describes the relationship between mRNA abundance, transcription rate, and degradation rate?

Accepted Answer

mRNA abundance = transcription rate / degradation rate

Question 5

In Drosophila, the sex determination pathway relies on alternative splicing of which three major genes?

Accepted Answer

Sex lethal (Sxl), transformer (tra), doublesex (dsx)

Question 6

Which of the following is a consequence of the c.840C\u003eT mutation in SMN2 compared to SMN1?

Accepted Answer

Exon 7 is frequently skipped in SMN2 transcripts, resulting in less functional SMN protein.

Question 7

The FDA-approved drug Spinraza treats spinal muscular atrophy by:

Accepted Answer

Binding to an intronic silencer site in SMN2 pre-mRNA, preventing hnRNP-A1 binding and promoting exon 7 inclusion.

Question 8

Which of the following best describes deadenylation-dependent mRNA decay?

Accepted Answer

Deadenylases shorten the poly(A) tail, reducing poly(A)-binding protein association and making the mRNA susceptible to exonuclease degradation.

Question 9

Which formula describes the half-life ($$t_{1/2}) of $$mRNA if the degradation rate constant is $$k$$?

Accepted Answer

$$t_{1/2} = \frac{\ln 2}{k}$$

Question 10

Which of the following is NOT a mechanism by which long noncoding RNAs (lncRNAs) regulate gene expression?

Accepted Answer

lncRNAs are translated into functional proteins that regulate transcription.

Question 11

Which of the following statements about the closed loop model of translation is correct?

Accepted Answer

Poly(A)-binding proteins interact with eIF4G, which binds eIF4E at the 5' cap, forming a loop that promotes translation initiation.

Question 12

Which of the following is a major function of the 5' m7G cap on eukaryotic mRNA?

Accepted Answer

It protects mRNA from 5'→3' exonuclease degradation and recruits cap-binding proteins for translation.

Question 13

Which of the following best explains how alternative polyadenylation can affect gene expression?

Accepted Answer

It can produce mRNAs with different 3' UTRs, altering mRNA stability, localization, or translation without changing the protein-coding sequence.

Question 14

Which of the following is a key feature of nonsense-mediated decay (NMD)?

Accepted Answer

It degrades mRNAs containing a premature termination codon (PTC) to prevent production of truncated proteins.

Question 15

Which of the following equations correctly represents the basic structure of the eukaryotic mRNA cap?

Accepted Answer

$$	ext{m}^7	ext{G}(5')	ext{--ppp--}(5')	ext{N--RNA--}3'$$

Question 16

Which of the following is a real-world example of a spliceopathy caused by disrupted splicing regulation?

Accepted Answer

Myotonic dystrophy, caused by repeat expansions that disrupt splicing regulation.

Question 17

Which of the following best describes the role of phosphorylation in posttranslational regulation?

Accepted Answer

Phosphorylation induces conformational changes in proteins, often altering their activity.

Question 18

Ubiquitin-mediated protein degradation involves which of the following steps?

Accepted Answer

Proteins are covalently modified with ubiquitin, recognized by the proteasome, and degraded into small peptides.

Posttranscriptional Regulation in Eukaryotes: Mechanisms and Implications

Study Guide - Practice Questions