DNA ISOLATION

*Question: What is the correct order of the molecular biology workflow?
A) Amplification → Extraction → Gel Electrophoresis → Quantification
B) Sample Collection → Nucleic Acid Extraction → Amplification → Quantification → Gel Electrophoresis → Downstream Applications
C) Sample Collection → Amplification → Extraction → Gel Electrophoresis
D) Nucleic Acid Extraction → Sample Collection → Quantification → PCR

*Answer: B) Sample Collection → Nucleic Acid Extraction → Amplification → Quantification → Gel Electrophoresis → Downstream Applications

*Question: What does DNA Isolation involve?
A) Only cell lysis to release DNA
B) Only purification of DNA from cellular components
C) Cell lysis (extraction) AND purification from other cellular components
D) Amplification and sequencing of DNA

*Answer: C) Cell lysis (extraction) AND purification from other cellular components

*Question: What is the goal of nucleic acid isolation?
A) To amplify DNA for PCR
B) To obtain pure, good quality and quantity nucleic acid
C) To sequence the genome
D) To separate RNA from DNA only

*Answer: B) To obtain pure, good quality and quantity nucleic acid

*Question: Which of the following is an example of a common contaminant removed during DNA purification?
A) Nucleotides and water
B) Proteins and Lipids
C) Salt and buffer
D) Primers and probes

*Answer: B) Proteins and Lipids

*Question: What is the basic first step in nucleic acid isolation?
A) Precipitation
B) Washing
C) Cell Lysis
D) Concentration

*Answer: C) Cell Lysis

*Question: Which step in nucleic acid isolation is considered OPTIONAL but important for downstream applications like PCR?
A) Cell Lysis
B) Separation
C) Purification
D) Concentration

*Answer: D) Concentration

*Question: Which of the following is a mechanical method of cell disruption?
A) SDS treatment
B) Proteinase K digestion
C) Vortexing with beads
D) CTAB treatment

*Answer: C) Vortexing with beads

*Question: What principle does the sonicator use to break down cells?
A) High pressure
B) Ultrasonic waves
C) Alkaline solution
D) Enzymatic digestion

*Answer: B) Ultrasonic waves

*Question: How does the High Pressure Homogenizer disrupt cells?
A) By using ultrasonic waves
B) By enzymatic digestion of the membrane
C) By forcing cells through narrow spaces causing rupture due to pressure changes
D) By freezing and thawing cells repeatedly

*Answer: C) By forcing cells through narrow spaces causing rupture due to pressure changes

*Question: What is the function of CTAB in chemical cell lysis?
A) Inhibits nucleases
B) Dissolves the membrane
C) Breaks disulfide bonds
D) Stabilizes nucleic acid

*Answer: B) Dissolves the membrane

*Question: What does CTAB stand for?
A) Cetyltetramethylammonium bromide
B) Cetyltrimethylammonium bromide
C) Chlorotrimethylammonium bromide
D) Cetyltriethylammonium bromide

*Answer: B) Cetyltrimethylammonium bromide

*Question: What does SDS stand for?
A) Sodium Dodecyl Sulfate
B) Sodium Disulfide Solution
C) Sodium Dextran Sulfite
D) Sodium Disodium Substrate

*Answer: A) Sodium Dodecyl Sulfate

*Question: What is the role of Beta-mercaptoethanol in DNA isolation?
A) Inhibits nucleases
B) Dissolves the cell membrane
C) Breaks down disulfide bonds of proteins
D) Stabilizes DNA in solution

*Answer: C) Breaks down disulfide bonds of proteins

*Question: What is the function of EDTA in nucleic acid isolation?
A) Dissolves lipids
B) Inhibits nucleases
C) Precipitates proteins
D) Stabilizes the cell membrane

*Answer: B) Inhibits nucleases

*Question: What is the role of sodium chloride in the lysis buffer?
A) Lyses the cell membrane
B) Inhibits protein activity
C) Stabilizes the nucleic acid
D) Breaks disulfide bonds

*Answer: C) Stabilizes the nucleic acid

*Question: Which enzyme is used for enzymatic lysis of ANIMAL cells?
A) Cellulase
B) Lyticase
C) Lysozyme
D) Proteinase K

*Answer: D) Proteinase K

*Question: Which enzyme is used for enzymatic lysis of PLANT cells?
A) Lysozyme
B) Cellulase
C) Proteinase K
D) Lyticase

*Answer: B) Cellulase

*Question: Which enzyme is used for enzymatic lysis of YEAST?
A) Lysozyme
B) Cellulase
C) Lyticase
D) Proteinase K

*Answer: C) Lyticase

*Question: Which enzyme is used for enzymatic lysis of BACTERIA?
A) Cellulase
B) Lyticase
C) Proteinase K
D) Lysozyme

*Answer: D) Lysozyme

*Question: Which of the following is NOT one of the 5 factors that influence the disruption strategy?
A) Stability of Molecules
B) Cell Membrane Type
C) Temperature of Sample
D) Presence of Inhibitors

*Answer: C) Temperature of Sample

*Question: What is the principle of centrifugation in nucleic acid isolation?
A) Separation based on charge
B) Separation based on size
C) Separation based on density
D) Separation based on solubility

*Answer: C) Separation based on density

*Question: Which chemicals are used in the denaturation and separation of biomolecules from nucleic acids?
A) EDTA and Tris
B) SDS, Phenol and Chloroform
C) Ethanol and isopropanol
D) NaOH and CTAB

*Answer: B) SDS, Phenol and Chloroform

*Question: What alcohol concentration is used in WASHING of precipitated nucleic acids?
A) 50-60% ethanol
B) 95-100% ethanol
C) 70-80% ethanol
D) 30-40% ethanol

*Answer: C) 70-80% ethanol

*Question: What alcohol concentration is used in PRECIPITATION of nucleic acids?
A) 70% ethanol
B) 95% absolute ethanol or isopropanol
C) 50% ethanol
D) 30% methanol

*Answer: B) 95% absolute ethanol or isopropanol

*Question: What is the purpose of the washing step in nucleic acid isolation?
A) To dissolve the DNA pellet
B) To amplify the nucleic acid
C) To remove remaining impurities or salts
D) To precipitate the nucleic acid

*Answer: C) To remove remaining impurities or salts

*Question: Why can air drying be used to remove ethanol after the wash step?
A) Ethanol is non-volatile
B) Ethanol is volatile and easily evaporates
C) Ethanol reacts with DNA during heating
D) Ethanol stabilizes the pellet at room temperature

*Answer: B) Ethanol is volatile and easily evaporates

*Question: At what temperature range is mild heating used to facilitate dissolution of the DNA pellet?
A) 37-42°C
B) 60-70°C
C) 50-55°C
D) 80-90°C

*Answer: C) 50-55°C

*Question: What is the recommended storage solution for nucleic acid stabilization?
A) Phosphate buffered saline
B) Normal saline
C) TE buffer
D) Distilled water

*Answer: C) TE buffer

*Question: At what temperatures should nucleic acids be stored for stability?
A) 25°C or -20°C
B) 5°C or -70°C
C) 37°C or -10°C
D) 4°C or -20°C

*Answer: B) 5°C or -70°C

*Question: What should be AVOIDED to maintain nucleic acid stability?
A) Aliquoting the sample
B) Using nuclease-free reagents
C) Freeze-thaw cycles
D) Storing in TE buffer

*Answer: C) Freeze-thaw cycles

*Question: What treatment is performed POST-DNA isolation if DNA was isolated?
A) DNAse treatment
B) RNAse treatment
C) Proteinase K treatment
D) Lysozyme treatment

*Answer: B) RNAse treatment

*Question: What treatment is performed POST-RNA isolation if RNA was isolated?
A) RNAse treatment
B) Lyticase treatment
C) DNAse treatment
D) Cellulase treatment

*Answer: C) DNAse treatment

*Question: Which method is used for quantification and purity check of nucleic acid?
A) PCR
B) NanoDrop
C) Gel Electrophoresis
D) CTAB extraction

*Answer: B) NanoDrop

*Question: What is gel electrophoresis used for in the molecular biology workflow?
A) Amplifying DNA
B) Quantifying DNA concentration
C) Checking integrity and size of DNA fragments
D) Purifying DNA from proteins

*Answer: C) Checking integrity and size of DNA fragments

*Question: Which of the following is a Chemical-based nucleic acid isolation method?
A) Spin columns
B) Magnetic bead-based kits
C) Phenol-chloroform extraction
D) Automated systems

*Answer: C) Phenol-chloroform extraction

*Question: Which of the following is a Solid-phase nucleic acid isolation method?
A) Alkaline extraction
B) CTAB extraction
C) GTPC extraction
D) Magnetic bead-based kits

*Answer: D) Magnetic bead-based kits

*Question: What does GTPC stand for?
A) Guanidinium-trichloride-phenol-chloroform
B) Guanidinium-thiocyanate-phenol-chloroform
C) Guanosine-thiocyanate-phenol-chloroform
D) Guanidinium-thiocyanate-phosphate-chloroform

*Answer: B) Guanidinium-thiocyanate-phenol-chloroform

*Question: In phenol-chloroform extraction, what is the aqueous phase compared to in blood separation?
A) Buffy coat
B) Packed RBCs
C) Plasma/serum
D) Clot

*Answer: C) Plasma/serum

*Question: What does the alkaline extraction method commonly isolate?
A) Genomic DNA from human cells
B) Plasmid DNA from bacteria
C) RNA from plant tissue
D) Mitochondrial DNA

*Answer: B) Plasmid DNA from bacteria

*Question: What alkaline solution is used in the alkaline extraction method?
A) KOH and CTAB
B) NaOH and SDS
C) Tris and EDTA
D) NaOH and chloroform

*Answer: B) NaOH and SDS

*Question: After neutralization in alkaline extraction, what happens to chromosomal DNA and proteins?
A) They remain in solution
B) They are eluted in the aqueous phase
C) They are precipitated
D) They bind to the spin column

*Answer: C) They are precipitated

*Question: Why is CTAB extraction widely used for plants?
A) Plant cells lack a nucleus
B) Plant cells contain large amounts of polysaccharides that can contaminate DNA
C) Plant DNA requires alkaline conditions
D) Plant cells are resistant to proteinase K

*Answer: B) Plant cells contain large amounts of polysaccharides that can contaminate DNA

*Question: What does CTAB do to plant polysaccharides during extraction?
A) Digests them enzymatically
B) Precipitates them with ethanol
C) Binds with them to allow DNA separation and purification
D) Dissolves them in chloroform

*Answer: C) Binds with them to allow DNA separation and purification

*Question: What dye is used in Cesium Chloride Gradient Centrifugation for DNA isolation?
A) Crystal violet
B) Methylene blue
C) Ethidium bromide
D) SYBR green

*Answer: C) Ethidium bromide

*Question: In Cesium Chloride Gradient Centrifugation, how is DNA separated?
A) By charge using ion exchange
B) By size using gel filtration
C) By density using ultracentrifugation
D) By affinity using silica columns

*Answer: C) By density using ultracentrifugation

*Question: How can the DNA bands be visualized in CsCl gradient centrifugation?
A) Visible light microscopy
B) Ultraviolet light
C) Infrared spectroscopy
D) NanoDrop

*Answer: B) Ultraviolet light

*Question: What are the 4 steps of the Solid-Phase Method in order?
A) Binding → Lysis → Washing → Elution
B) Lysis → Washing → Binding → Elution
C) Lysis → Binding → Washing → Elution
D) Washing → Lysis → Binding → Elution

*Answer: C) Lysis → Binding → Washing → Elution

*Question: In size exclusion by gel filtration, which molecules elute FIRST?
A) Small molecules that enter the pores
B) Large molecules that cannot enter the pores
C) Negatively charged molecules
D) DNA molecules bound to silica

*Answer: B) Large molecules that cannot enter the pores

*Question: In size exclusion by gel filtration, which molecules elute LAST?
A) Large molecules
B) Neutral molecules
C) Small molecules that enter the pores of the beads
D) Positively charged molecules

*Answer: C) Small molecules that enter the pores of the beads

*Question: What is the basis of separation in ion-exchange chromatography for DNA?
A) Molecular size
B) Specific binding interaction
C) Charge interaction
D) Density

*Answer: C) Charge interaction

*Question: Why does DNA bind to the anion exchange matrix?
A) DNA carries a positive charge due to its sugar backbone
B) DNA carries a negative charge due to its phosphate backbone
C) DNA is attracted to neutral silica
D) DNA forms hydrogen bonds with the matrix

*Answer: B) DNA carries a negative charge due to its phosphate backbone

*Question: How is purified DNA eluted from the anion exchange column?
A) By adding high salt buffer or acidic pH
B) By changing salt concentration or pH to release DNA from the matrix
C) By heating the column to 95°C
D) By adding phenol-chloroform

*Answer: B) By changing salt concentration or pH to release DNA from the matrix

*Question: In affinity chromatography using a silica-based column, under what condition does DNA bind to silica?
A) Low salt concentration
B) Neutral pH
C) High salt concentration
D) Alkaline pH

*Answer: C) High salt concentration

*Question: In affinity chromatography, what is used to elute the purified DNA from the silica column?
A) High salt buffer
B) Phenol-chloroform
C) Low salt buffer or water
D) 95% ethanol

*Answer: C) Low salt buffer or water

*Question: Which of the following is a human sample source for nucleic acid?
A) Fungi
B) Parasites
C) Saliva
D) Bacteria

*Answer: C) Saliva

*Question: Which of the following is a MICROORGANISM source of nucleic acid?
A) Hair
B) Blood
C) Skin
D) Virus

*Answer: D) Virus

*Question: What type of plasticware must be used in nucleic acid isolation to prevent degradation?
A) Standard laboratory grade plasticware
B) MolBio (Molecular Biology) grade plasticware
C) Any sterile plasticware
D) Autoclave-resistant plasticware

*Answer: B) MolBio (Molecular Biology) grade plasticware

*Question: What does TE buffer stand for in terms of its components?
A) Tris-EDTA buffer
B) Tris-Ethanol buffer
C) Tetracycline-EDTA buffer
D) Tris-Enzyme buffer

*Answer: A) Tris-EDTA buffer

*Question: What is the pH of the Tris buffer used in nucleic acid isolation?
A) pH 6
B) pH 7
C) pH 8
D) pH 9

*Answer: C) pH 8

*Question: Which two post-isolation methods are used to verify the quality and quantity of extracted DNA?
A) PCR and cloning
B) Gel Electrophoresis and NanoDrop
C) Centrifugation and precipitation
D) Southern blot and sequencing

*Answer: B) Gel Electrophoresis and NanoDrop

*Question: In the phenol-chloroform extraction, after centrifugation, which phase contains the RNA pellet?
A) Aqueous phase (top)
B) Interphase (middle)
C) Organic phase (bottom)
D) It is evenly distributed

*Answer: C) Organic phase (bottom)

*Question: Which of the following best describes the difference between DNA extraction and DNA purification?
A) Extraction removes proteins; purification breaks open cells
B) Extraction collects DNA by physical/chemical means; purification eliminates contamination from extracted DNA
C) Extraction and purification are the same process
D) Extraction uses enzymes; purification uses mechanical force

*Answer: B) Extraction collects DNA by physical/chemical means; purification eliminates contamination from extracted DNA

*Question: Which monovalent cations are used in nucleic acid precipitation?
A) Calcium chloride and magnesium sulfate
B) Ammonium, Potassium or Sodium Acetate, Lithium or Sodium Chloride
C) Iron sulfate and zinc chloride
D) Potassium permanganate and copper sulfate

*Answer: B) Ammonium, Potassium or Sodium Acetate, Lithium or Sodium Chloride

*Question: Which 3 principles are involved in the Solid-Phase Method?
A) Centrifugation, precipitation, and filtration
B) Size exclusion by gel filtration, ion-exchange chromatography, and affinity chromatography
C) Lysis, washing, and elution
D) Organic extraction, inorganic precipitation, and enzymatic digestion

*Answer: B) Size exclusion by gel filtration, ion-exchange chromatography, and affinity chromatography

*Question: Why is both quality AND quantity of extracted DNA important?
A) Low quantity DNA cannot be stored
B) High quality DNA cannot be amplified
C) Both are required to perform downstream applications like PCR successfully
D) Quantity determines purity of the sample

*Answer: C) Both are required to perform downstream applications like PCR successfully