Question 1

Which DNA repair mechanism is most commonly used in eukaryotic cells after a double-stranded break induced by CRISPR-Cas9, and what is a major consequence of this repair pathway?

Accepted Answer

Non-homologous end joining (NHEJ); it often creates indels that can disrupt gene function.

Question 2

A researcher wants to delete a gene using CRISPR-Cas9 to guarantee no functional protein is produced. Which strategy would be most effective?

Accepted Answer

Cutting at two sites flanking the gene to remove the entire coding region.

Question 3

What is the primary function of the Cas9 enzyme in bacterial cells?

Accepted Answer

To make double-stranded cuts in viral DNA, thereby killing viruses.

Question 4

Why is germline editing with CRISPR-Cas9 considered controversial?

Accepted Answer

Because edits in the germline can be passed on to future generations, potentially affecting the human gene pool.

Question 5

Which of the following best describes a monogenetic trait?

Accepted Answer

A trait determined by the genotype of a single gene, such as sickle cell anemia.

Question 6

In the context of CRISPR-based therapies for sickle cell anemia, why is it important that stem cells used for editing are autologous?

Accepted Answer

Because autologous cells come from the patient, reducing the risk of immune rejection.

Question 7

A CRISPR-Cas9 therapy for sickle cell anemia targets the BCL11A gene. What is the intended effect of reducing BCL11A activity?

Accepted Answer

To increase fetal hemoglobin expression, which prevents red blood cell sickling.

Question 8

Which equation best represents the process of base editing using a deaminase enzyme and a 'dead' Cas9 protein?

Accepted Answer

$$\mathrm{A} \rightarrow \mathrm{I} ($$Adenosine to Inosine)

Question 9

What is a major challenge in delivering CRISPR-Cas9 for treating inborn errors of metabolism in liver cells compared to sickle cell therapy?

Accepted Answer

Liver cells cannot be extracted and edited outside the body; delivery must occur in vivo.

Question 10

Which of the following is a potential risk associated with off-target effects of CRISPR-Cas9 editing?

Accepted Answer

Increased risk of cancer due to unintended mutations.

Question 11

Why do CRISPR-based therapies for sickle cell disease require a bone marrow transplant after editing?

Accepted Answer

To allow the edited stem cells to repopulate the blood system and produce healthy red blood cells.

Question 12

Which of the following best describes the difference between somatic and germline genome editing?

Accepted Answer

Somatic editing affects only the individual, while germline editing can be inherited by offspring.

Question 13

A patient with an inborn error of metabolism receives a CRISPR-based base editing therapy in the liver. What is a likely outcome if the editing is successful?

Accepted Answer

The patient can tolerate a higher protein diet and may reduce medication doses.

Question 14

Which of the following is NOT a reason why CRISPR-based therapies are currently expensive and slow to develop?

Accepted Answer

The rapid and simple approval process by regulatory agencies.

Question 15

Which of the following is a polygenetic trait?

Accepted Answer

Height

Question 16

What is the role of a guide RNA in the CRISPR-Cas9 system?

Accepted Answer

It determines the exact location where Cas9 will cut the DNA.

Question 17

Which of the following is a real-world application of CRISPR-Cas9 outside of human medicine?

Accepted Answer

Gene editing in honeybees for conservation biology.

Question 18

What is the main advantage of using a 'dead' Cas9 protein in CRISPR-based gene activation (CRISPRa)?

Accepted Answer

It can still recognize DNA and recruit transcription activators without cutting the DNA.

Question 19

Which of the following best explains why drug approval for CRISPR-based therapies takes a long time?

Accepted Answer

To ensure safety and efficacy through rigorous testing and regulation.

Genome Editing with CRISPR-Cas9: Mechanisms, Applications, and Implications

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