Biology Past Paper Review

**Group 6: Cytoplasmic Membrane Systems: Structure, Function, and Membrane Trafficking (10 Questions)** 1. **What is the primary function of the phospholipid bilayer in the plasma membrane?**\ A) Synthesize proteins\ B) Facilitate selective transport of molecules\ C) Store genetic...

**Group 6: Cytoplasmic Membrane Systems: Structure, Function, and Membrane Trafficking (10 Questions)** 1. **What is the primary function of the phospholipid bilayer in the plasma membrane?**\ A) Synthesize proteins\ B) Facilitate selective transport of molecules\ C) Store genetic information\ D) Generate energy for the cell\ **Correct Answer: B**\ **Rationalization:** The phospholipid bilayer acts as a semi-permeable barrier, regulating the transport of substances in and out of the cell. 2. **Which of the following organelles is involved in protein folding and modification?**\ A) Rough Endoplasmic Reticulum\ B) Mitochondria\ C) Lysosome\ D) Golgi apparatus\ **Correct Answer: A**\ **Rationalization:** The rough ER is studded with ribosomes and is responsible for the folding and post-translational modification of proteins. 3. **Clathrin-coated vesicles are involved in which cellular process?**\ A) Exocytosis\ B) Endocytosis\ C) Glycolysis\ D) Transcription\ **Correct Answer: B**\ **Rationalization:** Clathrin-coated vesicles are essential for endocytosis, where cells internalize molecules from their environment. 4. **Which process involves the movement of proteins from the ER to the Golgi apparatus?**\ A) Retrograde transport\ B) Anterograde transport\ C) Phagocytosis\ D) Autophagy\ **Correct Answer: B**\ **Rationalization:** Anterograde transport moves proteins from the ER to the Golgi for further modification. 5. **Lysosomes contain enzymes that perform which function?**\ A) Synthesize DNA\ B) Degrade cellular waste\ C) Produce ATP\ D) Synthesize lipids\ **Correct Answer: B**\ **Rationalization:** Lysosomes contain hydrolytic enzymes that break down cellular debris and waste materials. 6. **Which protein is responsible for vesicle formation during endocytosis?**\ A) Actin\ B) Tubulin\ C) Clathrin\ D) Myosin\ **Correct Answer: C**\ **Rationalization:** Clathrin plays a crucial role in vesicle formation by coating the vesicles during endocytosis. 7. **What is the function of SNARE proteins?**\ A) DNA replication\ B) Vesicle fusion\ C) ATP synthesis\ D) Ribosome assembly\ **Correct Answer: B**\ **Rationalization:** SNARE proteins mediate the fusion of vesicles with target membranes during exocytosis and membrane trafficking. 8. **The smooth endoplasmic reticulum is primarily involved in which activity?**\ A) Protein synthesis\ B) Lipid synthesis and detoxification\ C) DNA replication\ D) Glycolysis\ **Correct Answer: B**\ **Rationalization:** The smooth ER synthesizes lipids and detoxifies harmful substances within the cell. 9. **What is the role of COPI and COPII vesicles?**\ A) DNA repair\ B) Protein folding\ C) Transport between the ER and Golgi\ D) Energy production\ **Correct Answer: C**\ **Rationalization:** COPI and COPII vesicles mediate transport between the endoplasmic reticulum and the Golgi apparatus. 10. **Which type of membrane protein facilitates passive transport?**\ A) Channel proteins\ B) Glycoproteins\ C) Lipid rafts\ D) Clathrin\ **Correct Answer: A**\ **Rationalization:** Channel proteins allow ions and small molecules to passively diffuse across the membrane without energy expenditure. **Group 7: The Cytoskeleton and Cell Motility (10 Questions)** 11. **Which of the following cytoskeletal elements is primarily involved in maintaining cell shape and structure?**\ A) Microtubules\ B) Intermediate filaments\ C) Actin filaments\ D) Flagella\ **Correct Answer: B**\ **Rationalization:** Intermediate filaments provide mechanical support, maintaining cell shape and rigidity. 12. **Microtubules are composed of which protein subunit?**\ A) Actin\ B) Keratin\ C) Tubulin\ D) Myosin\ **Correct Answer: C**\ **Rationalization:** Tubulin is the protein that polymerizes to form microtubules, which are key for intracellular transport and cell division. 13. **What is the role of motor proteins like kinesin and dynein?**\ A) ATP synthesis\ B) DNA replication\ C) Transport of organelles along microtubules\ D) Synthesis of ribosomes\ **Correct Answer: C**\ **Rationalization:** Kinesin and dynein move along microtubules to transport organelles and vesicles within the cell. 14. **What structure forms the contractile ring during cytokinesis?**\ A) Actin filaments\ B) Microtubules\ C) Intermediate filaments\ D) Cilia\ **Correct Answer: A**\ **Rationalization:** Actin filaments assemble into a contractile ring that helps divide the cell during cytokinesis. 15. **Which cytoskeletal structure is responsible for the movement of cilia and flagella?**\ A) Microtubules\ B) Actin filaments\ C) Intermediate filaments\ D) Keratin filaments\ **Correct Answer: A**\ **Rationalization:** Microtubules form the core structure of cilia and flagella, enabling their movement. 16. **Which type of cell movement involves amoeboid motion?**\ A) Flagellar movement\ B) Microtubule sliding\ C) Actin polymerization\ D) Myosin contraction\ **Correct Answer: C**\ **Rationalization:** Amoeboid movement involves the extension of pseudopodia through actin polymerization. 17. **What is the primary function of the centrosome during cell division?**\ A) DNA replication\ B) Organizing the mitotic spindle\ C) Protein synthesis\ D) RNA transcription\ **Correct Answer: B**\ **Rationalization:** The centrosome organizes microtubules into the mitotic spindle, which separates chromosomes during mitosis. 18. **Which protein is critical for muscle contraction?**\ A) Tubulin\ B) Myosin\ C) Keratin\ D) Collagen\ **Correct Answer: B**\ **Rationalization:** Myosin interacts with actin filaments to cause muscle contraction. 19. **What role do intermediate filaments play in the cytoskeleton?**\ A) Facilitate intracellular transport\ B) Maintain mechanical strength\ C) Drive cell motility\ D) Generate ATP\ **Correct Answer: B**\ **Rationalization:** Intermediate filaments provide mechanical resilience to cells, helping them resist tension and compression. 20. **What cytoskeletal component makes up the nuclear lamina?**\ A) Microtubules\ B) Actin filaments\ C) Intermediate filaments\ D) Myosin filaments\ **Correct Answer: C**\ **Rationalization:** The nuclear lamina is composed of intermediate filaments, specifically lamin proteins, providing structural support to the nucleus. **Group 8: The Nature of the Gene and the Genome (10 Questions)** 21. **What is the basic unit of genetic information?**\ A) Codon\ B) Nucleotide\ C) Chromosome\ D) Gene\ **Correct Answer: D**\ **Rationalization:** A gene is a sequence of nucleotides in DNA that encodes the synthesis of a specific protein or RNA. 22. **Which of the following best describes a genome?**\ A) A set of amino acids in a protein\ B) A segment of RNA\ C) The complete set of DNA in an organism\ D) A collection of ribosomes\ **Correct Answer: C**\ **Rationalization:** The genome is the entire set of genetic material in an organism, encompassing all of its DNA. 23. **What is the difference between an exon and an intron?**\ A) Exons are non-coding regions, introns code for proteins\ B) Exons code for proteins, introns are non-coding regions\ C) Both are non-coding regions\ D) Both are protein-coding regions\ **Correct Answer: B**\ **Rationalization:** Exons are expressed as part of the final mRNA and code for proteins, whereas introns are spliced out during RNA processing. 24. **Which type of DNA is inherited maternally in eukaryotic organisms?**\ A) Nuclear DNA\ B) Mitochondrial DNA\ C) Chloroplast DNA\ D) Plasmid DNA\ **Correct Answer: B**\ **Rationalization:** Mitochondrial DNA is inherited exclusively from the mother and contains genes important for cellular respiration. 25. **What role do histones play in eukaryotic cells?**\ A) They assist in DNA replication\ B) They help package DNA into chromatin\ C) They catalyze RNA transcription\ D) They are involved in protein degradation\ **Correct Answer: B**\ **Rationalization:** Histones are proteins that help condense DNA into chromatin, making it more compact and regulating gene expression. 26. **Which process results in the formation of haploid cells from diploid cells?**\ A) Mitosis\ B) Meiosis\ C) Transcription\ D) DNA replication\ **Correct Answer: B**\ **Rationalization:** Meiosis reduces the chromosome number by half, producing haploid gametes (sperm and eggs). 27. **Which of the following is a result of alternative splicing?**\ A) Multiple genes are produced from a single mRNA transcript\ B) A single gene can code for multiple proteins\ C) DNA mutations are repaired\ D) The start codon is removed from mRNA\ **Correct Answer: B**\ **Rationalization:** Alternative splicing allows different combinations of exons to be joined, enabling a single gene to produce multiple protein isoforms. 28. **What is the central dogma of molecular biology?**\ A) RNA → DNA → Protein\ B) DNA → RNA → Protein\ C) Protein → DNA → RNA\ D) RNA → Protein → DNA\ **Correct Answer: B**\ **Rationalization:** The central dogma describes the flow of genetic information from DNA to RNA to protein. 29. **Which of the following sequences would be complementary to the DNA strand 5'-ATCGTACG-3'?**\ A) 5'-CGTACGAT-3'\ B) 5'-TACGATGC-3'\ C) 3'-TAGCATGC-5'\ D) 3'-TACGATGC-5'\ **Correct Answer: C**\ **Rationalization:** The complementary strand to 5'-ATCGTACG-3' would be 3'-TAGCATGC-5', as A pairs with T, and C pairs with G. 30. **Which of the following is NOT part of a nucleotide?**\ A) Phosphate group\ B) Ribose or deoxyribose sugar\ C) Nitrogenous base\ D) Amino acid\ **Correct Answer: D**\ **Rationalization:** A nucleotide consists of a phosphate group, a sugar, and a nitrogenous base. Amino acids are the building blocks of proteins, not nucleotides. **Group 9: The Central Dogma: DNA to RNA to Protein (10 Questions)** 31. **Which enzyme synthesizes RNA from a DNA template?**\ A) DNA polymerase\ B) RNA polymerase\ C) Ligase\ D) Primase\ **Correct Answer: B**\ **Rationalization:** RNA polymerase synthesizes RNA during transcription, using DNA as a template. 32. **What is the role of the promoter in transcription?**\ A) Terminates RNA synthesis\ B) Binds to ribosomes during translation\ C) Initiates transcription by binding RNA polymerase\ D) Signals the start of DNA replication\ **Correct Answer: C**\ **Rationalization:** The promoter is a DNA sequence that binds RNA polymerase, initiating transcription. 33. **Which of the following is a post-transcriptional modification in eukaryotes?**\ A) Polyadenylation\ B) DNA methylation\ C) Protein folding\ D) Chromosome condensation\ **Correct Answer: A**\ **Rationalization:** Polyadenylation adds a poly-A tail to the 3' end of mRNA, protecting it from degradation and facilitating export from the nucleus. 34. **What is the function of tRNA in translation?**\ A) Synthesizes proteins\ B) Carries amino acids to the ribosome\ C) Transcribes DNA into RNA\ D) Modifies proteins post-translation\ **Correct Answer: B**\ **Rationalization:** Transfer RNA (tRNA) brings the appropriate amino acids to the ribosome based on the codon sequence during translation. 35. **Which type of RNA is translated into a protein?**\ A) rRNA\ B) tRNA\ C) mRNA\ D) siRNA\ **Correct Answer: C**\ **Rationalization:** Messenger RNA (mRNA) carries the genetic code from DNA and is translated into proteins. 36. **What is the start codon for translation?**\ A) UAA\ B) AUG\ C) UAG\ D) UGA\ **Correct Answer: B**\ **Rationalization:** The codon AUG serves as the start codon and codes for methionine, initiating translation. 37. **Which of the following is NOT a stop codon?**\ A) UAG\ B) UAA\ C) UGA\ D) UAC\ **Correct Answer: D**\ **Rationalization:** UAG, UAA, and UGA are stop codons, while UAC codes for tyrosine. 38. **What is the role of the ribosome in protein synthesis?**\ A) Synthesizes mRNA\ B) Assembles amino acids into a polypeptide chain\ C) Binds to DNA during replication\ D) Modifies proteins post-translation\ **Correct Answer: B**\ **Rationalization:** The ribosome reads mRNA and assembles amino acids into a polypeptide chain during translation. 39. **During translation, peptide bonds are formed between which molecules?**\ A) DNA strands\ B) RNA nucleotides\ C) Amino acids\ D) Ribosomes\ **Correct Answer: C**\ **Rationalization:** Peptide bonds link amino acids together to form a protein. 40. **In eukaryotic cells, where does transcription occur?**\ A) Cytoplasm\ B) Nucleus\ C) Ribosome\ D) Golgi apparatus\ **Correct Answer: B**\ **Rationalization:** Transcription occurs in the nucleus, where DNA is housed, and mRNA is then exported to the cytoplasm for translation. **Group 10: Control of Gene Expression (5 Questions)** 41. **Which of the following is a mechanism for regulating gene expression in eukaryotes?**\ A) RNA splicing\ B) DNA replication\ C) Protein degradation\ D) Glycolysis\ **Correct Answer: A**\ **Rationalization:** RNA splicing can alter the mRNA transcript, influencing which proteins are produced and regulating gene expression. 42. **What is the role of transcription factors?**\ A) Catalyze the replication of DNA\ B) Facilitate the binding of RNA polymerase to DNA\ C) Degrade mRNA\ D) Act as ribosomal proteins\ **Correct Answer: B**\ **Rationalization:** Transcription factors assist in the initiation of transcription by helping RNA polymerase bind to specific promoter regions on the DNA. 43. **Which term describes a gene that is always expressed at a constant level?**\ A) Inducible gene\ B) Repressible gene\ C) Constitutive gene\ D) Epigenetic gene\ **Correct Answer: C**\ **Rationalization:** A constitutive gene is expressed at a constant level under normal conditions, without the need for regulation. 44. **How does methylation of DNA typically affect gene expression?**\ A) It enhances transcription\ B) It silences genes\ C) It promotes RNA splicing\ D) It increases translation\ **Correct Answer: B**\ **Rationalization:** DNA methylation generally suppresses gene expression by preventing transcription factors from binding to the DNA. 45. **Which molecule can block mRNA translation by binding to it?**\ A) tRNA\ B) microRNA (miRNA)\ C) DNA polymerase\ D) Ribosomal RNA\ **Correct Answer: B**\ **Rationalization:** MicroRNAs (miRNAs) can bind to complementary mRNA sequences and inhibit their translation, thereby regulating gene expression. **Group 11: DNA Replication and Repair (5 Questions)** 46. **Which enzyme is responsible for unwinding the DNA double helix during replication?**\ A) DNA polymerase\ B) Helicase\ C) Ligase\ D) Primase\ **Correct Answer: B**\ **Rationalization:** Helicase unwinds the DNA double helix, creating single-stranded templates for replication. 47. **What is the function of DNA polymerase?**\ A) Unwind the DNA strand\ B) Add nucleotides to a growing DNA strand\ C) Seal gaps in the DNA backbone\ D) Synthesize RNA primers\ **Correct Answer: B**\ **Rationalization:** DNA polymerase adds nucleotides to the growing strand of DNA during replication, synthesizing a complementary strand. 48. **Which process repairs damage to a single base in DNA?**\ A) Base excision repair\ B) Nucleotide excision repair\ C) Mismatch repair\ D) Homologous recombination\ **Correct Answer: A**\ **Rationalization:** Base excision repair corrects damage to individual bases caused by oxidation, alkylation, or deamination. 49. **What is the role of ligase in DNA replication?**\ A) Synthesizes RNA primers\ B) Seals gaps between Okazaki fragments\ C) Unwinds the DNA double helix\ D) Adds nucleotides to the 3\' end of the DNA strand\ **Correct Answer: B**\ **Rationalization:** DNA ligase seals the gaps between Okazaki fragments on the lagging strand during DNA replication. 50. **Which enzyme is involved in correcting mismatches during DNA replication?**\ A) Helicase\ B) DNA polymerase\ C) Topoisomerase\ D) Ligase\ **Correct Answer: B**\ **Rationalization:** DNA polymerase has proofreading activity, which allows it to correct mismatches during replication. **Group 12: Cell Division (10 Questions)** 51. **What are the two main stages of the cell cycle?**\ A) Interphase and cytokinesis\ B) Mitosis and meiosis\ C) Interphase and mitosis\ D) S phase and G phase\ **Correct Answer: C**\ **Rationalization:** The cell cycle consists of interphase (the preparation phase) and mitosis (the division phase), which is followed by cytokinesis. 52. **During which phase of mitosis do sister chromatids separate?**\ A) Prophase\ B) Metaphase\ C) Anaphase\ D) Telophase\ **Correct Answer: C**\ **Rationalization:** Sister chromatids are pulled apart and move to opposite poles of the cell during anaphase. 53. **Which of the following occurs during prophase?**\ A) Chromosomes are duplicated\ B) The nuclear envelope begins to reform\ C) Chromatin condenses into visible chromosomes\ D) DNA is replicated\ **Correct Answer: C**\ **Rationalization:** During prophase, chromatin condenses into visible chromosomes, and the nuclear envelope starts to break down. 54. **What is the purpose of the spindle fibers during mitosis?**\ A) To synthesize DNA\ B) To replicate chromosomes\ C) To separate and move chromosomes\ D) To form the nuclear envelope\ **Correct Answer: C**\ **Rationalization:** Spindle fibers attach to chromosomes and help separate them during mitosis. 55. **What is the end result of mitosis?**\ A) Four genetically identical cells\ B) Two genetically identical cells\ C) Two genetically different cells\ D) Four genetically different cells\ **Correct Answer: B**\ **Rationalization:** Mitosis results in two genetically identical daughter cells from a single parent cell. 56. **What occurs during cytokinesis?**\ A) DNA replication\ B) Chromosome alignment\ C) Separation of the cytoplasm\ D) Nuclear envelope formation\ **Correct Answer: C**\ **Rationalization:** Cytokinesis is the process of dividing the cytoplasm, resulting in two distinct daughter cells. 57. **In which phase of meiosis do homologous chromosomes separate?**\ A) Meiosis I\ B) Meiosis II\ C) Both meiosis I and II\ D) Interphase\ **Correct Answer: A**\ **Rationalization:** Homologous chromosomes are separated during meiosis I, resulting in two haploid cells. 58. **What is the significance of crossing over during meiosis?**\ A) It creates identical gametes\ B) It increases genetic variation\ C) It ensures proper chromosome separation\ D) It results in DNA replication\ **Correct Answer: B**\ **Rationalization:** Crossing over exchanges genetic material between homologous chromosomes, increasing genetic variation among gametes. 59. **Which of the following statements about meiosis is true?**\ A) It produces diploid cells\ B) It consists of one round of cell division\ C) It produces four haploid cells\ D) It occurs in somatic cells\ **Correct Answer: C**\ **Rationalization:** Meiosis involves two rounds of cell division and produces four genetically diverse haploid cells (gametes). 60. **What is the role of the checkpoints in the cell cycle?**\ A) To ensure that cells are properly divided\ B) To facilitate DNA replication\ C) To detect errors and prevent the progression of the cell cycle\ D) To assist in protein synthesis\ **Correct Answer: C**\ **Rationalization:** Checkpoints monitor the cell cycle and ensure that any errors, such as DNA damage, are corrected before the cell proceeds to the next phase. **Group 13: Cell Signaling and Signal Transduction: Communication between Cells (10 Questions)** 61. **What is the primary function of signal transduction pathways?**\ A) To synthesize proteins\ B) To transport molecules across the cell membrane\ C) To convert an extracellular signal into a cellular response\ D) To replicate DNA\ **Correct Answer: C**\ **Rationalization:** Signal transduction pathways convert external signals into internal responses, enabling cells to react to their environment. 62. **Which type of signaling occurs between cells that are in close proximity?**\ A) Endocrine signaling\ B) Paracrine signaling\ C) Autocrine signaling\ D) Synaptic signaling\ **Correct Answer: B**\ **Rationalization:** Paracrine signaling involves the release of signaling molecules that affect neighboring cells. 63. **What is the role of receptors in cell signaling?**\ A) To synthesize proteins\ B) To bind and respond to signaling molecules\ C) To transport ions across membranes\ D) To replicate DNA\ **Correct Answer: B**\ **Rationalization:** Receptors are proteins that bind to specific signaling molecules, initiating a signal transduction cascade within the cell. 64. **Which of the following is a common second messenger in cell signaling?**\ A) ATP\ B) cAMP\ C) NADPH\ D) RNA\ **Correct Answer: B**\ **Rationalization:** Cyclic AMP (cAMP) acts as a second messenger that transmits signals within the cell following receptor activation. 65. **What type of signaling involves the release of hormones into the bloodstream?**\ A) Autocrine signaling\ B) Paracrine signaling\ C) Endocrine signaling\ D) Juxtacrine signaling\ **Correct Answer: C**\ **Rationalization:** Endocrine signaling involves hormones being released into the bloodstream, affecting distant target cells. 66. **What is the effect of a ligand binding to its receptor?**\ A) It always initiates cell division\ B) It causes the receptor to undergo a conformational change\ C) It prevents the activation of intracellular enzymes\ D) It promotes apoptosis\ **Correct Answer: B**\ **Rationalization:** Ligand binding causes receptors to change shape, activating the receptor and triggering downstream signaling pathways. 67. **Which of the following processes can lead to signal amplification in cells?**\ A) Phosphorylation cascades\ B) Autocrine signaling\ C) Endocytosis\ D) Protein synthesis\ **Correct Answer: A**\ **Rationalization:** Phosphorylation cascades amplify the signal as one activated protein can activate multiple downstream targets. 68. **What is a common outcome of cell signaling?**\ A) Synthesis of nucleic acids\ B) Alteration of gene expression\ C) Replication of DNA\ D) Degradation of proteins\ **Correct Answer: B**\ **Rationalization:** Cell signaling often results in changes in gene expression, allowing the cell to respond appropriately to various stimuli. 69. **In which type of signaling do cells respond to signals they release themselves?**\ A) Endocrine signaling\ B) Paracrine signaling\ C) Autocrine signaling\ D) Juxtacrine signaling\ **Correct Answer: C**\ **Rationalization:** Autocrine signaling involves a cell responding to signaling molecules it has produced, affecting itself. 70. **Which structure is primarily involved in synaptic signaling?**\ A) Hormones\ B) Neurotransmitters\ C) Cytokines\ D) Growth factors\ **Correct Answer: B**\ **Rationalization:** Synaptic signaling involves neurotransmitters being released from one neuron to transmit a signal to another neuron across a synapse. **Group 14: Cancer (10 Questions)** 71. **What characterizes a cancer cell compared to a normal cell?**\ A) They grow and divide uncontrollably\ B) They have a fixed lifespan\ C) They exhibit contact inhibition\ D) They differentiate into specialized cells\ **Correct Answer: A**\ **Rationalization:** Cancer cells grow and divide without the normal regulatory signals that control cell proliferation. 72. **Which of the following is a common characteristic of tumors?**\ A) They only grow in specific organs\ B) They are always benign\ C) They can invade surrounding tissues\ D) They do not require a blood supply\ **Correct Answer: C**\ **Rationalization:** Tumors can invade nearby tissues and may metastasize to other parts of the body. 73. **What is the role of oncogenes in cancer?**\ A) They repair damaged DNA\ B) They promote cell growth and division\ C) They induce apoptosis\ D) They inhibit tumor growth\ **Correct Answer: B**\ **Rationalization:** Oncogenes are mutated forms of normal genes (proto-oncogenes) that promote excessive cell growth and division, contributing to cancer development. 74. **What is the purpose of a biopsy in cancer diagnosis?**\ A) To visualize tumors on imaging scans\ B) To remove and analyze tissue for cancer cells\ C) To assess the effectiveness of chemotherapy\ D) To measure tumor markers in blood\ **Correct Answer: B**\ **Rationalization:** A biopsy involves extracting tissue samples to examine for the presence of cancer cells, confirming a cancer diagnosis. 75. **Which of the following is a common treatment for cancer?**\ A) Antibiotics\ B) Radiotherapy\ C) Antiviral drugs\ D) Immunization\ **Correct Answer: B**\ **Rationalization:** Radiotherapy uses high-energy radiation to kill cancer cells or shrink tumors, and is a common treatment option for many types of cancer. **Group 15: Techniques in Cell and Molecular Biology (10 Questions)** 76. **Which technique is used to amplify a specific DNA segment?**\ A) Gel electrophoresis\ B) Polymerase chain reaction (PCR)\ C) Southern blotting\ D) Cloning\ **Correct Answer: B**\ **Rationalization:** PCR is a technique used to rapidly amplify specific DNA sequences, making millions of copies of a target segment. 77. **What does gel electrophoresis separate based on?**\ A) Size and charge of nucleic acids\ B) Sequence of nucleotides\ C) Protein structure\ D) Cell type\ **Correct Answer: A**\ **Rationalization:** Gel electrophoresis separates nucleic acids based on their size and charge, allowing visualization of DNA or RNA fragments. 78. **Which technique allows for the visualization of gene expression in a tissue?**\ A) Immunofluorescence\ B) In situ hybridization\ C) Western blotting\ D) RT-PCR\ **Correct Answer: B**\ **Rationalization:** In situ hybridization is used to detect specific RNA or DNA sequences in their native locations within tissue sections. 79. **What is the purpose of a Western blot?**\ A) To visualize DNA\ B) To detect specific proteins\ C) To analyze RNA expression\ D) To measure enzyme activity\ **Correct Answer: B**\ **Rationalization:** Western blotting is a technique used to detect and quantify specific proteins in a sample using antibodies. 80. **Which of the following is a common method for gene editing?**\ A) CRISPR-Cas9\ B) PCR\ C) DNA sequencing\ D) Electrophoresis\ **Correct Answer: A**\ **Rationalization:** CRISPR-Cas9 is a revolutionary gene-editing technology that allows for precise modifications of DNA in organisms. 81. **What is the role of reverse transcriptase in molecular biology?**\ A) It amplifies DNA\ B) It converts RNA into DNA\ C) It synthesizes proteins\ D) It repairs DNA\ **Correct Answer: B**\ **Rationalization:** Reverse transcriptase is an enzyme that synthesizes complementary DNA (cDNA) from an RNA template. 82. **Which technique is used to sequence DNA?**\ A) Sanger sequencing\ B) Northern blotting\ C) RT-PCR\ D) Southern blotting\ **Correct Answer: A**\ **Rationalization:** Sanger sequencing is a method used to determine the nucleotide sequence of DNA. 83. **What does the term \"transfection\" refer to?**\ A) The uptake of DNA by bacteria\ B) The introduction of nucleic acids into eukaryotic cells\ C) The separation of proteins by size\ D) The amplification of DNA sequences\ **Correct Answer: B**\ **Rationalization:** Transfection refers to the process of introducing nucleic acids (such as DNA or RNA) into eukaryotic cells to study gene function and expression. 84. **What is a common application of CRISPR technology?**\ A) Protein purification\ B) DNA amplification\ C) Gene knockout or modification\ D) RNA sequencing\ **Correct Answer: C**\ **Rationalization:** CRISPR technology is widely used for gene knockout or modification, allowing researchers to study gene function and create genetically modified organisms.