Molecular Biology & CRISPR Technology 2026 Guide

1. What is the fundamental mechanism of the CRISPR-Cas9 system? A) Protein-based transcription repression B) RNA-guided DNA cleavage and repair C) Random mutation induction via UV radiation D) Polymerase chain reaction (PCR) amplification Correct Answer: B) RNA-guided DNA cleavage and repair 2. Which molecule acts as the "GPS" that guides the Cas9 nuclease to the specific target DNA sequence? A) mRNA B) gRNA (guide RNA) C) tRNA D) DNA polymerase Correct Answer: B) gRNA (guide RNA) 3. What does "PAM" stand for in the context of CRISPR? A) Protospacer Adjacent Motif B) Protein Assembly Mechanism C) Polymerase Activation Molecule D) Primary Alignment Matrix Correct Answer: A) Protospacer Adjacent Motif 4. What is the primary role of the PAM sequence? A) It initiates DNA transcription B) It allows Cas9 to distinguish between the host DNA and the viral target DNA C) It stabilizes the double-stranded DNA structure D) It acts as a stop codon Correct Answer: B) It allows Cas9 to distinguish between the host DNA and the viral target DNA 5. How do cells typically repair the double-strand breaks (DSBs) caused by Cas9? A) Only through homologous recombination B) Through Non-Homologous End Joining (NHEJ) or Homology-Directed Repair (HDR) C) By producing new organelles D) By RNA interference Correct Answer: B) Through Non-Homologous End Joining (NHEJ) or Homology-Directed Repair (HDR) 6. Which repair pathway is more likely to create "knockout" mutations through insertions or deletions? A) HDR B) NHEJ C) Transcription-Coupled Repair D) Base Excision Repair Correct Answer: B) NHEJ 7. "Prime Editing" is a 2026-refined technique known for: A) Its high error rate B) Ability to perform precise substitutions, insertions, and deletions without double-strand breaks C) Requiring massive amounts of ATP D) Being exclusively for viral genome editing Correct Answer: B) Ability to perform precise substitutions, insertions, and deletions without double-strand breaks 8. What is the main purpose of "Base Editing"? A) Deleting whole chromosomes B) Directly converting one nucleotide base into another (e.g., C to T) without breaking the DNA backbone C) Creating protein arrays D) Amplifying gene expression Correct Answer: B) Directly converting one nucleotide base into another without breaking the DNA backbone 9. "Off-target effects" in CRISPR refer to: A) The intended mutation sites B) Unintended editing at DNA sites that resemble the target sequence C) Cell death due to high concentrations of Cas9 D) Successful gene correction Correct Answer: B) Unintended editing at DNA sites that resemble the target sequence 10. What is "Epigenetic Editing"? A) Changing the DNA sequence itself B) Modifying gene expression (e.g., via methylation) without changing the underlying DNA sequence C) Deleting entire introns D) Replacing mitochondrial DNA Correct Answer: B) Modifying gene expression without changing the underlying DNA sequence 11. CRISPR-mediated "Gene Drives" are used to: A) Increase the speed of DNA replication in a laboratory B) Force a genetic trait to spread through a population at a rate higher than Mendelian inheritance C) Prevent viral replication in humans D) Store genetic data in hard drives Correct Answer: B) Force a genetic trait to spread through a population at a rate higher than Mendelian inheritance 12. Why are "Gene Drives" ethically controversial? A) They are too expensive to implement B) Potential irreversible impacts on ecological balance and biodiversity C) They are illegal in all countries D) They interfere with computer hardware Correct Answer: B) Potential irreversible impacts on ecological balance and biodiversity 13. "Ex vivo" gene therapy involves: A) Injecting CRISPR directly into the patient's body B) Extracting cells, editing them in the laboratory, and re-infusing them into the patient C) Editing the DNA of a virus D) Using CRISPR to treat plants only Correct Answer: B) Extracting cells, editing them in the laboratory, and re-infusing them into the patient 14. What is "in vivo" gene therapy? A) Editing cells in a petri dish B) Direct delivery of the CRISPR machinery into the patient's body C) Editing mitochondrial DNA only D) Culturing bacteria in a lab Correct Answer: B) Direct delivery of the CRISPR machinery into the patient's body 15. Which delivery system is most commonly used for in vivo CRISPR applications? A) Lipid nanoparticles or AAV (Adeno-Associated Virus) vectors B) Metal needles C) Heat shock D) Electroporation Correct Answer: A) Lipid nanoparticles or AAV vectors 16. What is "Germline Editing"? A) Editing non-heritable somatic cells B) Editing embryos, sperm, or eggs, resulting in changes passed to future generations C) Editing bacteria in the gut D) Cleaning the laboratory equipment Correct Answer: B) Editing embryos, sperm, or eggs, resulting in changes passed to future generations 17. Why is germline editing globally restricted? A) It is biologically impossible B) Profound bioethical concerns regarding "designer babies" and potential unintended hereditary consequences C) It lacks scientific interest D) It is only useful for plants Correct Answer: B) Profound bioethical concerns regarding "designer babies" and potential unintended hereditary consequences 18. What is the central dogma of molecular biology? A) DNA - RNA - Protein B) Protein - RNA - DNA C) DNA - Protein - RNA D) RNA - DNA - Protein Correct Answer: A) DNA - RNA - Protein 19. What is an "intron"? A) A coding region of DNA B) A non-coding region of DNA that is removed during mRNA processing C) A protein structure in the nucleus D) A type of ribosome Correct Answer: B) A non-coding region of DNA that is removed during mRNA processing 20. What is an "exon"? A) A protein involved in DNA repair B) A coding region of DNA that remains in the mature mRNA C) A non-coding region removed during splicing D) A virus that infects bacteria Correct Answer: B) A coding region of DNA that remains in the mature mRNA 21. "Alternative splicing" explains why: A) Humans have more proteins than genes B) DNA replicates itself C) Bacteria are resistant to antibiotics D) CRISPR is inefficient Correct Answer: A) Humans have more proteins than genes 22. In 2026, "Multiplexing" with CRISPR refers to: A) Editing multiple genes simultaneously using multiple gRNAs B) Increasing the speed of DNA sequencing C) Combining different delivery vectors D) Using multiple types of Cas proteins Correct Answer: A) Editing multiple genes simultaneously using multiple gRNAs 23. "CRISPR-Cas12" often differs from Cas9 in that it: A) Targets RNA instead of DNA B) Recognizes T-rich PAM sequences and has different cleavage kinetics C) Does not require a gRNA D) Is smaller but less accurate Correct Answer: B) Recognizes T-rich PAM sequences and has different cleavage kinetics 24. "Dideoxynucleotide" sequencing (Sanger) is based on: A) The termination of DNA synthesis using chain-terminating nucleotides B) Real-time fluorescent imaging C) RNA folding patterns D) Protein synthesis rates Correct Answer: A) The termination of DNA synthesis using chain-terminating nucleotides 25. "Next-Generation Sequencing" (NGS) allows for: A) Single molecule sequencing at high speed B) Massive parallel sequencing of millions of DNA fragments C) Visualizing chromosomes under a light microscope D) Only protein sequencing Correct Answer: B) Massive parallel sequencing of millions of DNA fragments 26. What is a "Transcription Factor"? A) An enzyme that cuts DNA B) A protein that regulates gene expression by binding to specific DNA sequences C) A molecule that transports RNA D) A type of cell membrane receptor Correct Answer: B) A protein that regulates gene expression by binding to specific DNA sequences 27. "Chromatin" is composed of: A) Only DNA B) DNA tightly coiled around histone proteins C) Ribosomes and tRNA D) Lipid bilayers Correct Answer: B) DNA tightly coiled around histone proteins 28. "Epigenetic methylation" of DNA typically results in: A) Gene activation B) Gene silencing C) Accelerated replication D) DNA repair Correct Answer: B) Gene silencing 29. "CRISPR-a" (CRISPR activation) uses: A) Catalytically dead Cas9 (dCas9) fused to transcriptional activators B) Active Cas9 to delete DNA C) RNA interference D) Standard Cas9 for DNA cutting Correct Answer: A) Catalytically dead Cas9 (dCas9) fused to transcriptional activators 30. "CRISPR-i" (CRISPR interference) uses: A) dCas9 fused to repressors to block transcription B) Standard Cas9 to cut the DNA C) gRNA to degrade mRNA D) High-speed PCR Correct Answer: A) dCas9 fused to repressors to block transcription 31. "Cas13" is a CRISPR protein that targets: A) Double-stranded DNA B) Single-stranded RNA C) Proteins directly D) Cell membranes Correct Answer: B) Single-stranded RNA 32. "Xenotransplantation" (e.g., using CRISPR to modify pig organs) aims to: A) Create faster pigs B) Reduce immunological rejection in human organ transplantation C) Study viral evolution D) Create bioluminescent organs Correct Answer: B) Reduce immunological rejection in human organ transplantation 33. "Microbiome editing" with CRISPR could potentially: A) Cure infectious diseases by targeting specific gut bacteria B) Alter human height C) Change blood type D) Replace lost limbs Correct Answer: A) Cure infectious diseases by targeting specific gut bacteria 34. "Chimeric Antigen Receptor T-cell" (CAR-T) therapy sometimes uses CRISPR to: A) Make T-cells kill viruses only B) Enhance the precision and potency of T-cells against cancer cells C) Reduce the cost of chemotherapy D) Edit patient sperm cells Correct Answer: B) Enhance the precision and potency of T-cells against cancer cells 35. What is the role of "Reverse Transcriptase"? A) Synthesizing RNA from a DNA template B) Synthesizing DNA from an RNA template C) Splicing introns D) Repairing DSBs Correct Answer: B) Synthesizing DNA from an RNA template