Question 1

Which of the following best explains why eukaryotic gene expression is more complex than prokaryotic gene expression?

Accepted Answer

Eukaryotes have gene-sparse genomes, multiple RNA polymerases, and lack operons, requiring more intricate regulatory mechanisms.

Question 2

A researcher discovers a eukaryotic gene that is not expressed unless a specific protein binds to a DNA sequence far upstream of the gene. Which regulatory element is most likely involved?

Accepted Answer

Enhancer

Question 3

Which of the following statements about chromatin remodeling in eukaryotes is correct?

Accepted Answer

Chromatin remodeling structures (CRS) reposition nucleosomes, making DNA binding sites accessible for transcription.

Question 4

The GAL4p protein in yeast is an example of which type of transcriptional regulator, and what is its mechanism of action?

Accepted Answer

It is an activator protein that binds to a specific promoter sequence, recruiting transcriptional machinery via zinc ion-mediated binding in the major groove of DNA.

Question 5

Which of the following best describes the effect of DNA methylation at CpG islands in eukaryotic gene regulation?

Accepted Answer

Methylation of cytosine in CpG islands generally reduces transcription by promoting chromatin compaction.

Question 6

A mutation prevents the removal of the poly-A tail from an mRNA transcript. What is the most likely consequence for this mRNA?

Accepted Answer

The mRNA will persist longer in the cytoplasm, potentially producing more polypeptide.

Question 7

Which of the following is true regarding alternative splicing in eukaryotes?

Accepted Answer

Alternative splicing generates different isoforms by removing internal exons, but cannot remove terminal exons.

Question 8

In the context of RNA interference (RNAi), what is the role of the Dicer enzyme?

Accepted Answer

Dicer cleaves double-stranded RNA into fragments of about 25 nucleotides.

Question 9

A scientist is studying a gene that is silenced in Drosophila due to the action of Polycomb group proteins. What is the most likely mechanism of this silencing?

Accepted Answer

Polycomb group proteins cause compaction of histones, blocking gene expression.

Question 10

Which of the following best describes the process of imprinting in eukaryotic gene regulation?

Accepted Answer

Imprinting involves differential methylation of certain genes during gametogenesis, leading to parent-of-origin specific gene expression.

Question 11

A eukaryotic gene is transcribed at a high rate only when multiple enhancer sequences are present. What is the most likely explanation for this observation?

Accepted Answer

Multiple enhancers increase the recruitment of transcription factors, thereby increasing the transcriptional rate.

Question 12

Which of the following scenarios best illustrates the concept of autoregulation in eukaryotic gene expression?

Accepted Answer

A gene product negatively regulates its own expression by interacting with intermediates in its pathway, as seen with cmyc.

Question 13

If a eukaryotic mRNA is rapidly degraded after its poly-A tail is shortened to 30 nucleotides, which process is most likely responsible?

Accepted Answer

Deadenylation-dependent decay

Question 14

A mutation in the gene encoding the TATA-binding protein (TBP) would most directly affect which step of eukaryotic gene expression?

Accepted Answer

Recruitment of RNA polymerase to the promoter

Question 15

Which of the following best describes the fate of the guide and passenger strands during RNA interference (RNAi)?

Accepted Answer

The guide strand is incorporated into the RISC complex, while the passenger strand is degraded.

Question 16

A patient has a genetic disorder caused by improper imprinting, resulting in the expression of both maternal and paternal alleles of a gene that is normally imprinted. Which of the following best explains the molecular basis of this disorder?

Accepted Answer

Failure to methylate the gene during gametogenesis, leading to loss of parent-of-origin specific expression.

Question 17

Which of the following equations best represents the relationship between mRNA stability and polypeptide production in eukaryotic cells?

Accepted Answer

$$N_{polypeptide} = k 	imes t_{mRNA}$$

Question 18

A eukaryotic gene is silenced throughout embryogenesis but is later expressed in the germ line after methylation marks are erased. Which process does this scenario best illustrate?

Accepted Answer

Imprinting

Question 19

Which of the following best explains why cloning animals using somatic cell nuclear transfer can be problematic with respect to gene expression?

Accepted Answer

Imprinted genes may retain methylation patterns from the donor cell, leading to abnormal gene expression in the clone.

Eukaryotic Gene Regulation and Expression

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