Gene editing represents a monumental leap in biotechnology, offering the potential to precisely modify an organism’s DNA. Technologies like CRISPR-Cas9 have moved from complex laboratory tools to the forefront of clinical research, promising novel treatments for genetic diseases once considered incurable. For PharmD students, understanding the mechanisms, applications, and challenges of gene editing is crucial for comprehending this new wave of personalized and potentially curative therapies.
1. What is the primary function of the Cas9 protein in the CRISPR-Cas9 system?
- It acts as a guide to find the target DNA sequence
- It functions as a nuclease to create a double-strand break in the DNA
- It provides the template for repairing the DNA break
- It transports the editing machinery into the nucleus
Answer: It functions as a nuclease to create a double-strand break in the DNA
2. In the CRISPR-Cas9 gene editing system, what is the primary function of the guide RNA (gRNA)?
- To act as the nuclease that cuts the DNA
- To provide the template for DNA repair
- To direct the Cas9 nuclease to a specific target sequence in the DNA
- To permanently integrate into the host genome
Answer: To direct the Cas9 nuclease to a specific target sequence in the DNA
3. The cellular DNA repair pathway that is error-prone and often results in small insertions or deletions (indels) is called:
- Homology Directed Repair (HDR)
- Base Excision Repair (BER)
- Non-Homologous End Joining (NHEJ)
- Mismatch Repair (MMR)
Answer: Non-Homologous End Joining (NHEJ)
4. To precisely replace a mutated gene sequence with a corrected one using CRISPR, which cellular repair mechanism must be active?
- Non-Homologous End Joining (NHEJ)
- Homology Directed Repair (HDR)
- Single-Strand Annealing (SSA)
- The CRISPR system provides its own repair mechanism
Answer: Homology Directed Repair (HDR)
5. What is the main difference between somatic cell gene editing and germline gene editing?
- Somatic editing is temporary, while germline editing is permanent
- Somatic editing targets non-reproductive cells and is not heritable, while germline editing is heritable
- Somatic editing is less efficient than germline editing
- Somatic editing can only be performed ex vivo
Answer: Somatic editing targets non-reproductive cells and is not heritable, while germline editing is heritable
6. Zinc-Finger Nucleases (ZFNs) and TALENs are earlier gene-editing tools that both utilize which nuclease to cut DNA?
- Cas9
- Cas12a
- Cpf1
- FokI
Answer: FokI
7. A major advantage of the CRISPR-Cas9 system compared to ZFNs and TALENs is:
- It is much less efficient at cutting DNA
- The ease of programming its target specificity by simply changing the guide RNA sequence
- It does not cause double-strand breaks
- It has no risk of off-target effects
Answer: The ease of programming its target specificity by simply changing the guide RNA sequence
8. The term “off-target effect” in gene editing refers to:
- The failure of the editing tool to enter the target cell
- The editing machinery cutting DNA at an unintended location in the genome
- The therapeutic effect wearing off too quickly
- The patient developing an immune response to the therapy
Answer: The editing machinery cutting DNA at an unintended location in the genome
9. In an ex vivo gene editing therapy approach:
- The editing tools are injected directly into the patient’s bloodstream
- A topical cream containing the editing tools is applied to the skin
- Patient’s cells are removed, edited in a lab, and then infused back into the patient
- The editing is performed on a close relative of the patient
Answer: Patient’s cells are removed, edited in a lab, and then infused back into the patient
10. CAR-T cell therapy can be created using gene editing to:
- Modify a patient’s T-cells to recognize and attack cancer cells
- Make cancer cells more susceptible to chemotherapy
- Correct the genetic defect within the tumor itself
- Deliver a radioactive isotope to the tumor
Answer: Modify a patient’s T-cells to recognize and attack cancer cells
11. The PAM (Protospacer Adjacent Motif) sequence is a short DNA sequence that is required for:
- The guide RNA to fold correctly
- The Cas9 nuclease to bind and cut the target DNA
- The cell to initiate Homology Directed Repair
- The delivery vehicle to enter the cell
Answer: The Cas9 nuclease to bind and cut the target DNA
12. A “gene knockout” is typically achieved by leveraging which repair pathway after a double-strand break?
- Homology Directed Repair (HDR)
- Non-Homologous End Joining (NHEJ)
- Nucleotide Excision Repair (NER)
- Base Excision Repair (BER)
Answer: Non-Homologous End Joining (NHEJ)
13. Which of the following is a significant challenge for in vivo gene editing therapies?
- The difficulty of delivering the editing machinery to the specific target tissue in the body
- The simplicity of the delivery process
- The lack of any potential side effects
- The editing tools are too stable and last forever
Answer: The difficulty of delivering the editing machinery to the specific target tissue in the body
14. Base editing is a newer form of gene editing that differs from standard CRISPR-Cas9 in that it:
- Creates a double-strand break to initiate repair
- Chemically converts one DNA base to another without making a double-strand break
- Can only be used to delete entire genes
- Works on RNA instead of DNA
Answer: Chemically converts one DNA base to another without making a double-strand break
15. The discovery of the CRISPR system as a gene-editing tool was adapted from its natural function in which organisms?
- Plants
- Humans
- Fungi
- Bacteria and archaea
Answer: Bacteria and archaea
16. Which of the following is an example of a monogenic disease that is a primary target for gene editing therapies?
- Influenza
- Type 2 Diabetes
- Sickle Cell Disease
- Hypertension
Answer: Sickle Cell Disease
17. The use of adeno-associated virus (AAV) vectors to deliver CRISPR components in vivo raises what potential safety concern?
- The vector cannot enter human cells
- The patient may develop an immune response to the AAV capsid proteins
- The AAV vector is too small to carry any genetic material
- The AAV vector is a rapidly replicating virus
Answer: The patient may develop an immune response to the AAV capsid proteins
18. How does gene editing fundamentally differ from RNAi-based therapies?
- Gene editing modifies the cell’s permanent DNA, while RNAi targets transient mRNA molecules
- RNAi modifies the cell’s DNA, while gene editing targets mRNA
- Gene editing can only be used to upregulate genes
- There is no fundamental difference
Answer: Gene editing modifies the cell’s permanent DNA, while RNAi targets transient mRNA molecules
19. In ZFN and TALEN systems, the DNA-binding domain is composed of _________, while the DNA-cleaving domain is the ________ nuclease.
- protein; Cas9
- RNA; FokI
- protein; FokI
- RNA; Cas9
Answer: protein; FokI
20. The primary ethical argument against germline gene editing in humans is that:
- It is not technologically possible
- The genetic changes would be passed on to subsequent generations
- It is too expensive
- It is less effective than somatic editing
Answer: The genetic changes would be passed on to subsequent generations
21. A “gene drive” is a potential application of gene editing that:
- Ensures a specific edited gene is preferentially inherited, spreading it through a population
- Turns off all genes in an organism simultaneously
- Is a type of delivery vehicle for CRISPR
- Is a computer program for designing guide RNAs
Answer: Ensures a specific edited gene is preferentially inherited, spreading it through a population
22. A major focus of current research is to develop Cas enzymes with novel PAM requirements in order to:
- Increase the number of potential target sites in the genome
- Decrease the efficiency of gene editing
- Ensure the enzyme only cuts in one specific location in all genomes
- Make the enzyme larger and more immunogenic
Answer: Increase the number of potential target sites in the genome
23. Prime editing is an advanced gene editing technique that uses a reverse transcriptase to:
- “Search and replace” a gene sequence without requiring a double-strand break or a separate donor template
- Create many double-strand breaks simultaneously
- Delete an entire chromosome
- Silence a target mRNA molecule
Answer: “Search and replace” a gene sequence without requiring a double-strand break or a separate donor template
24. The success of ex vivo gene editing for sickle cell disease involves editing which type of cells?
- Red blood cells
- Liver cells
- Hematopoietic stem cells
- Neurons
Answer: Hematopoietic stem cells
25. A significant hurdle in translating gene editing from the lab to the clinic is:
- A lack of diseases to target
- Ensuring long-term safety and efficacy in human patients
- The refusal of all scientists to work on the technology
- The simplicity of the regulatory process
Answer: Ensuring long-term safety and efficacy in human patients
26. What component of the CRISPR system makes it so easily programmable?
- The complex protein structure of Cas9
- The simplicity of synthesizing a specific guide RNA sequence
- The requirement of the FokI nuclease
- The use of lipid nanoparticles
Answer: The simplicity of synthesizing a specific guide RNA sequence
27. What is the result of using Non-Homologous End Joining (NHEJ) to repair a double-strand break within the coding region of a gene?
- A perfect correction of the original sequence
- A frameshift mutation that typically inactivates the gene
- The insertion of a new, functional gene
- The gene becomes more stable
Answer: A frameshift mutation that typically inactivates the gene
28. An in vivo gene editing therapy for an inherited retinal disease would likely be administered via:
- An oral tablet
- A direct injection into the eye
- An intravenous infusion
- A topical cream
Answer: A direct injection into the eye
29. Compared to traditional gene therapy (gene addition), a key advantage of gene editing is the ability to:
- Correct a mutated gene at its original location in the genome
- Only add new genes, not correct existing ones
- Integrate randomly throughout the genome
- Deliver much larger pieces of DNA
Answer: Correct a mutated gene at its original location in the genome
30. The “Cas” in CRISPR-Cas9 stands for:
- Cellular associated sequence
- CRISPR associated
- Catalytic assisting sequence
- Chromosome assembly system
Answer: CRISPR associated
31. Why must ZFNs and TALENs be used in pairs?
- To increase the chance of off-target effects
- The FokI nuclease they use must dimerize (form a pair) to become active and cut the DNA
- One nuclease cuts the sense strand and the other cuts the antisense strand
- It is a regulatory requirement that has no scientific basis
Answer: The FokI nuclease they use must dimerize (form a pair) to become active and cut the DNA
32. A pharmacist’s role regarding future gene editing therapies will likely include:
- Performing the gene editing procedures in the pharmacy
- Educating patients on the complex science, potential benefits, and risks of the therapy
- Designing the guide RNA sequences for new treatments
- Ignoring these therapies as they are outside the scope of pharmacy
Answer: Educating patients on the complex science, potential benefits, and risks of the therapy
33. The development of “high-fidelity” Cas9 variants is aimed at:
- Increasing the speed of DNA cutting
- Reducing off-target cleavage to improve safety
- Making the enzyme less specific
- Allowing the enzyme to function without a guide RNA
Answer: Reducing off-target cleavage to improve safety
34. A major difference between ZFNs/TALENs and CRISPR is that ZFNs and TALENs recognize DNA using ________ domains, while CRISPR uses ________.
- protein; guide RNA
- RNA; guide protein
- lipid; guide RNA
- protein; guide protein
Answer: protein; guide RNA
35. Delivering the CRISPR-Cas9 system as an mRNA for Cas9 and a separate gRNA molecule is a strategy to:
- Make the editing effect permanent
- Reduce the duration of the editing machinery in the cell, potentially lowering off-target risks
- Ensure the components integrate into the DNA
- Avoid the need for a lipid nanoparticle
Answer: Reduce the duration of the editing machinery in the cell, potentially lowering off-target risks
36. A “transgenic animal” created for research is often made using which technology?
- Gene editing tools like CRISPR-Cas9
- RNA interference
- Small molecule inhibitors
- Monoclonal antibodies
Answer: Gene editing tools like CRISPR-Cas9
37. The natural purpose of the CRISPR system in bacteria is to:
- Repair its own DNA
- Provide a defense mechanism against invading viruses (bacteriophages)
- Regulate its metabolism
- Allow it to communicate with other bacteria
Answer: Provide a defense mechanism against invading viruses (bacteriophages)
38. One method to check for off-target effects after a gene editing experiment is:
- Polymerase Chain Reaction (PCR)
- Western Blotting
- Whole-genome sequencing
- ELISA
Answer: Whole-genome sequencing
39. A potential future application of in vivo gene editing could be targeting the PCSK9 gene in liver cells to:
- Treat muscular dystrophy
- Permanently lower LDL cholesterol
- Correct the mutation for cystic fibrosis
- Cure HIV infection
Answer: Permanently lower LDL cholesterol
40. The specificity of CRISPR-Cas9 editing is primarily dependent on the:
- Type of cell being targeted
- Sequence of the guide RNA
- Concentration of the Cas9 protein
- Brand of the laboratory equipment used
Answer: Sequence of the guide RNA
41. For gene editing therapies to become widespread, a significant challenge to overcome is:
- Manufacturing and cost
- A lack of scientific interest
- The absence of any genetic diseases to treat
- The refusal of the FDA to consider them
Answer: Manufacturing and cost
42. A “knock-in” mouse model created with CRISPR would be designed to:
- Delete a specific gene
- Introduce a specific mutation or insert a new gene at a precise location
- Cause random mutations throughout the genome
- Silence a gene at the mRNA level
Answer: Introduce a specific mutation or insert a new gene at a precise location
43. A key logistical issue for ex vivo gene therapies like CAR-T is:
- The simplicity of the manufacturing process
- The long-term stability of the product at room temperature
- The complex and patient-specific manufacturing and supply chain
- The ability to treat thousands of patients from a single batch
Answer: The complex and patient-specific manufacturing and supply chain
44. What does HDR require that NHEJ does not?
- A double-strand break
- The Cas9 enzyme
- A DNA repair template
- A guide RNA
Answer: A DNA repair template
45. Which of the following diseases would be the most difficult to treat with a single gene editing therapy?
- Sickle Cell Disease (caused by a single gene mutation)
- Cystic Fibrosis (caused by mutations in a single gene)
- Huntington’s Disease (caused by a single gene mutation)
- Type 2 Diabetes (a complex, polygenic disease with lifestyle factors)
Answer: Type 2 Diabetes (a complex, polygenic disease with lifestyle factors)
46. The term “safe harbor” in the context of gene editing refers to:
- A location in the genome where a gene can be inserted with minimal risk of disrupting other genes
- A method for delivering the Cas9 protein
- A type of guide RNA
- A legal protection for scientists
Answer: A location in the genome where a gene can be inserted with minimal risk of disrupting other genes
47. The length of the guide RNA’s targeting sequence (typically ~20 nucleotides) is a key factor in determining the system’s:
- Potency
- Stability
- Specificity
- Size
Answer: Specificity
48. Why is editing hematopoietic stem cells (HSCs) a promising strategy for blood disorders?
- HSCs are easy to access from the bloodstream
- HSCs are the precursor cells that give rise to all mature blood cells
- HSCs do not have a nucleus
- HSCs are resistant to all forms of gene editing
Answer: HSCs are the precursor cells that give rise to all mature blood cells
49. An potential immunogenic response to the Cas9 protein could lead to:
- An enhanced editing effect
- The patient’s immune system clearing the editing machinery before it can work
- A permanent change in the patient’s blood type
- A reduction in the cost of therapy
Answer: The patient’s immune system clearing the editing machinery before it can work
50. The ultimate promise of gene editing as a therapeutic modality is the potential to:
- Manage the symptoms of genetic diseases
- Provide a one-time, potentially curative treatment for genetic diseases
- Replace all small molecule drugs
- Make diseases more severe
Answer: Provide a one-time, potentially curative treatment for genetic diseases
I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.
Mail- Sachin@pharmacyfreak.com