Question 1

Which of the following best describes the process of alternative splicing in eukaryotic cells?

Accepted Answer

It allows a single pre-mRNA to be spliced in different ways, producing multiple protein isoforms from one gene.

Question 2

A mutation causes an intron to be retained in the mature mRNA of a plant gene. What is the most likely consequence?

Accepted Answer

The intron will be translated, potentially altering the protein sequence and function.

Question 3

Which of the following mechanisms is responsible for the removal of the 5' cap from mRNA, leading to its degradation?

Accepted Answer

The decapping enzyme

Question 4

A researcher observes that a tumor suppressor gene in bladder cancer is inactivated in one allele by mutation and in the other by hypermethylation. What is the most likely outcome?

Accepted Answer

The cell will escape cell cycle control and may divide uncontrollably.

Question 5

Which of the following best explains why humans can produce over 290,000 different proteins from only about 20,000 genes?

Accepted Answer

Alternative splicing allows for multiple protein isoforms from a single gene.

Question 6

Which of the following statements about DNA methylation is correct?

Accepted Answer

Hypermethylation of CpG islands in promoters generally silences gene expression.

Question 7

A mouse with the agouti (A) allele shows a yellow coat color. What epigenetic modification is most likely associated with increased yellow pigment?

Accepted Answer

Hypomethylation of the agouti gene promoter

Question 8

Which of the following is a function of non-coding RNAs (ncRNAs) in epigenetic regulation?

Accepted Answer

They can act as decoys, guides, adapters, or enhancers to regulate transcription.

Question 9

Which of the following best describes the role of histone acetylation in gene expression?

Accepted Answer

It relaxes chromatin structure, making genes more accessible for transcription.

Question 10

A nonsense mutation introduces a premature stop codon into an mRNA. Which cellular mechanism is most likely to target this mRNA for degradation?

Accepted Answer

Nonsense-mediated decay (NMD)

Question 11

In the context of mRNA localization, what is the function of the 'zip code' sequence in actin mRNA?

Accepted Answer

It binds to ZBP1, which transports the mRNA to the cell's leading edge and blocks translation until localization is complete.

Question 12

Which of the following best explains how maternal nurturing in mice can affect the stress response of their offspring through epigenetic mechanisms?

Accepted Answer

High maternal nurturing leads to DNA hypomethylation and histone acetylation, increasing GR expression and stress adaptation.

Question 13

Which of the following is a direct effect of cytoplasmic polyadenylation on mRNA translation?

Accepted Answer

Elongation of the poly-A tail allows poly-A binding proteins and translation initiation factors to bind, promoting translation.

Question 14

Which of the following statements about epigenetic modifications is correct?

Accepted Answer

They are reversible chemical modifications to DNA or histones that regulate gene expression.

Question 15

A cell is observed to have increased levels of 5-methylcytosine (5mC) in the promoter region of a gene. What is the most likely effect on gene expression?

Accepted Answer

Gene expression will decrease due to transcriptional silencing.

Question 16

Which enzyme is responsible for digesting mRNA from the 5' to 3' direction after decapping?

Accepted Answer

XRN1 exoribonuclease

Question 17

Which of the following scenarios best illustrates the concept of mutually exclusive exons?

Accepted Answer

Inclusion of one exon in the mature mRNA leads to the exclusion of another exon from the same cluster.

Question 18

Which of the following is a likely consequence of global hypomethylation in cancer cells?

Accepted Answer

Unrestricted transcription, activation of transposable elements, and increased genome instability.

Question 19

Which of the following best describes the role of processing (P) bodies in the cytoplasm?

Accepted Answer

They are localized centers for mRNA decay containing decapping enzymes and exoribonucleases.

Question 20

A patient has a mutation in the calcitonin gene that affects alternative splicing. Which of the following is a possible outcome?

Accepted Answer

The gene may produce either calcitonin or CGRP, depending on the splicing pattern.

Post-Transcriptional Regulation and Epigenetics in Eukaryotes

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