Question 1

Which of the following best describes the function of the signal recognition particle (SRP) during cotranslational import into the endoplasmic reticulum (ER)?

Accepted Answer

SRP binds to the ER signal sequence and blocks translation until the ribosome docks on the ER membrane.

Question 2

In the lac operon, what is the effect of a mutation in the operator (lacO) that prevents the repressor from binding?

Accepted Answer

The operon is continuously expressed, even in the absence of lactose.

Question 3

Which equation best represents the exponential amplification of DNA fragments during PCR, where $$n is $$the number of cycles?

Accepted Answer

$$2^n$$

Question 4

Which regulatory mechanism is most commonly used in bacteria to turn genes OFF?

Accepted Answer

Negative regulation, where a regulatory protein binds to turn the gene OFF.

Question 5

What is the role of cAMP and CAP in the positive regulation of the lac operon?

Accepted Answer

cAMP binds to CAP, which then binds to the promoter and increases transcription when glucose is absent.

Question 6

Which of the following is a real-world application of RT-PCR?

Accepted Answer

Detecting whether a specific mRNA is being expressed in a cell.

Question 7

Which of the following statements about CpG islands is correct?

Accepted Answer

CpG islands are often located near promoters of housekeeping genes and are usually not methylated.

Question 8

A mutation in the lacI gene results in a nonfunctional repressor. What is the expected outcome for the lac operon?

Accepted Answer

The operon is expressed regardless of the presence or absence of lactose.

Question 9

Which of the following best describes the function of ARE (AU-rich elements) in eukaryotic mRNA?

Accepted Answer

AREs promote rapid degradation of mRNA.

Question 10

Which of the following is a consequence of histone deacetylation in eukaryotic gene regulation?

Accepted Answer

Chromatin compaction and transcriptional silencing.

Question 11

In the trp operon, what happens when tryptophan is present in the cell?

Accepted Answer

Tryptophan acts as a co-repressor, activating the repressor to bind the operator and inhibit transcription.

Question 12

Which motif is commonly found in transcription factors and allows for DNA binding?

Accepted Answer

Helix-turn-helix motif

Question 13

Which of the following best explains why the poly-A tail is important for mRNA stability?

Accepted Answer

A longer poly-A tail increases mRNA stability by protecting it from degradation.

Question 14

Which of the following is a key difference between negative and positive regulation of gene expression?

Accepted Answer

Negative regulation turns genes OFF, while positive regulation turns genes ON.

Question 15

Which process allows a single gene to produce multiple protein products in eukaryotes?

Accepted Answer

Alternative splicing

Question 16

Which of the following is a function of miRNAs in eukaryotic cells?

Accepted Answer

miRNAs induce mRNA degradation or translational repression.

Question 17

Which of the following best describes the effect of a mutation in the promoter (Plac) of the lac operon?

Accepted Answer

RNA polymerase cannot bind, so none of the lac operon genes are transcribed.

Question 18

Which of the following is a real-world consequence of a mutation in a restriction endonuclease recognition site?

Accepted Answer

The enzyme cannot cut the DNA at the mutated site, affecting cloning or gene mapping experiments.

Question 19

Which of the following best describes the role of transcription factors in eukaryotic gene regulation?

Accepted Answer

Transcription factors bind to response elements and regulate the rate of transcription.

Gene Regulation in Prokaryotes and Eukaryotes: Operons, Regulatory Mechanisms, and Molecular Biology Techniques

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