Question 1

Which of the following best describes the mechanism by which CRISPR-Cas9 introduces targeted changes in the genome?

Accepted Answer

CRISPR-Cas9 uses a guide RNA to direct the Cas9 nuclease to a specific DNA sequence, where it creates a double-strand break.

Question 2

Which of the following is a key difference between Non-Homologous End Joining (NHEJ) and Homologous Recombination (HR) in DNA repair after CRISPR-Cas9 cleavage?

Accepted Answer

NHEJ is error-prone and can introduce insertions or deletions, while HR is highly faithful and uses a homologous template for repair.

Question 3

A patient with sickle cell disease is treated with a CRISPR-based therapy that disrupts the BCL11A gene. What is the intended therapeutic effect of this gene edit?

Accepted Answer

Increase fetal hemoglobin production to compensate for defective adult hemoglobin.

Question 4

Which of the following statements about the origins of the CRISPR-Cas system is correct?

Accepted Answer

It originated as an adaptive immune defense mechanism in prokaryotes.

Question 5

A researcher wants to knock out a gene in human cells using genome editing. Which of the following tools would be most appropriate for this purpose?

Accepted Answer

CRISPR-Cas9 with a guide RNA targeting the gene of interest.

Question 6

Which of the following best explains why cells lacking the CCR5 receptor are resistant to HIV infection?

Accepted Answer

HIV requires the CCR5 receptor to enter host cells; without it, the virus cannot bind and infect.

Question 7

Which of the following equations represents the Hardy-Weinberg equilibrium for a gene with two alleles, A and a, with frequencies $$p$$ and $$q$$?

Accepted Answer

$$p^2 + 2pq$$ + $$q^2 = 1$

Question 8

A new gene therapy for congenital amaurosis uses CRISPR to correct a mutation in a gene required for photoreceptor function. What is the most likely outcome of successful therapy?

Accepted Answer

Restoration of the ability of rod and cone cells to detect light and transmit electrical signals.

Question 9

Which of the following is a major advantage of CRISPR-Cas9 over Zinc Finger Nucleases (ZFNs) and TALENs for genome editing?

Accepted Answer

CRISPR-Cas9 uses a simple guide RNA for targeting, making it easier to design and implement.

Question 10

A tomato has been genetically modified to increase anthocyanin levels by inserting a gene from snapdragon. Which of the following best describes this process?

Accepted Answer

Transgenic modification using gene insertion to enhance a nutritional trait.

Question 11

Which of the following best describes a 'knock-in' mutation generated by genome editing?

Accepted Answer

Insertion of a new gene or DNA sequence at a specific locus.

Question 12

Which of the following is a real-world example of precision medicine enabled by genome editing?

Accepted Answer

Using CRISPR to correct the sickle cell mutation in a patient's hematopoietic stem cells.

Question 13

Which of the following is a potential ethical concern associated with germline genome editing?

Accepted Answer

Heritable changes may be passed to future generations without their consent.

Question 14

A patient with beta-thalassemia is treated with a CRISPR-based therapy that targets the HBB gene. Which of the following best describes the goal of this therapy?

Accepted Answer

To correct the mutation in the HBB gene and restore normal hemoglobin production.

Question 15

Which of the following best explains why the efficiency of 'knock-in' mutations using CRISPR-Cas9 is typically less than 10%?

Accepted Answer

Homologous recombination, required for knock-in, is less efficient than non-homologous end joining.

Question 16

Which of the following is a plausible reason why a population may deviate from Hardy-Weinberg equilibrium?

Accepted Answer

Non-random mating or selection alters allele frequencies.

Question 17

Which of the following best describes the role of guide RNA (gRNA) in the CRISPR-Cas9 system?

Accepted Answer

It directs the Cas9 nuclease to a specific DNA sequence for cleavage.

Question 18

A scientist is using TALENs to edit a gene in a plant. Which of the following components is essential for TALEN function?

Accepted Answer

A fusion of a DNA-binding domain derived from TALEs and a nuclease domain.

Question 19

Which of the following best explains why CRISPR-based therapies for blood disorders are considered a breakthrough in medicine?

Accepted Answer

They allow for precise correction of disease-causing mutations at the DNA level.

CRISPR-Cas and Genome Editing: Principles, Tools, and Applications in Genetics

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